Blackrock Muniholdings Investment Quality Fund (MFL) NPORT-P BlackRock MuniHoldings Investment Quality Fund (May 2021 report)

Schedule of Investments  (unaudited) May 31, 2021 BlackRock MuniHoldings Investment Quality Fund (MFL) (Percentages shown are based on Net Assets)

Security	Par (000)		Value
Municipal Bonds
Alabama — 0.3%
Selma Industrial Development Board, RB, Series A, 5.38%, 12/01/35	$	1,745	$	1,786,548
Arizona — 4.4%
Arizona Industrial Development Authority, RB(a) 4.38%, 07/01/39		1,015		1,090,790
Series A, 5.00%, 07/01/39		855		909,181
Series A, 5.00%, 07/01/49		965		1,014,958
Series A, 5.00%, 07/01/54		745		780,708
Industrial Development Authority of the County of Pima, RB, 5.00%, 06/15/47(a)		1,480		1,512,279
Industrial Development Authority of the County of Pima, Refunding RB, 5.00%, 06/15/52(a)		825		865,103
Maricopa County Industrial Development Authority, Refunding RB
5.00%, 07/01/39(a)		360		421,531
5.00%, 07/01/54(a)		820		931,709
Series A, 5.00%, 01/01/38		3,000		3,628,410
Salt River Project Agricultural Improvement & Power District, RB, 4.00%, 01/01/41		10,000		12,040,300
University of Arizona, Refunding RB, Series A, 5.00%, 06/01/40		2,300		2,684,651
				25,879,620
Arkansas — 0.5%
Arkansas Development Finance Authority, RB, AMT, 4.50%, 09/01/49(a)		2,395		2,632,009
California — 15.8%
California Community Housing Agency, RB, Series A-2, 4.00%, 08/01/47(a)		2,380		2,582,895
California Community Housing Agency, RB, M/F Housing, Series A, 5.00%, 04/01/49(a)		370		421,352
California State Public Works Board, RB
Series B, 4.00%, 05/01/46		5,500		6,632,780
Series F, 5.25%, 09/01/33		3,240		3,593,549
Series I, 5.50%, 11/01/30		4,500		5,054,850
Series I, 5.50%, 11/01/33		2,000		2,242,780
California State University, Refunding RB, Series A, 5.00%, 11/01/42		3,500		4,321,590
City of Los Angeles Department of Airports, ARB, Series A, AMT, 5.00%, 05/15/42		1,750		2,097,095
City of Los Angeles Department of Airports, Refunding ARB, Series A, AMT, 5.00%, 05/15/46		10,000		12,789,800
Golden State Tobacco Securitization Corp., Refunding RB
Series A-1, 5.00%, 06/01/47		2,880		2,980,483
Series A-2, 5.00%, 06/01/47		785		812,389
Los Angeles Unified School District GO, Series C, 4.00%, 07/01/37		5,000		6,084,850
Manteca Financing Authority, RB, Series A, (AGC-ICC), 5.75%, 12/01/36		3,285		3,298,830
Regents of the University of California Medical Center Pooled Revenue, Refunding RB, Series J, 5.25%, 05/15/38		2,705		2,952,291

Security	Par (000)		Value
California (continued)
San Francisco City & County Airport Comm-San Francisco International Airport, Refunding ARB
Series A, AMT, 5.25%, 05/01/33	$	6,370	$	6,941,453
Series A, AMT, 5.00%, 05/01/38		3,040		3,815,170
Series A, AMT, 5.00%, 05/01/44		3,430		3,849,352
Series B, AMT, 5.00%, 05/01/46		7,855		9,295,528
University of California, Refunding RB, Series AR, 5.00%, 05/15/38		10,200		12,343,836
				92,110,873
Colorado — 3.1%
City & County of Denver Colorado Airport System Revenue, ARB
Series A, AMT, 5.50%, 11/15/28		2,700		3,022,947
Series A, AMT, 5.50%, 11/15/30		1,040		1,162,803
Series A, AMT, 5.50%, 11/15/31		1,250		1,396,700
City & County of Denver Colorado Airport System Revenue, Refunding ARB, Series A, AMT, 5.00%, 12/01/43		10,500		12,748,365
				18,330,815
Connecticut — 2.5%
Connecticut State Health & Educational Facilities Authority, RB, Series A-1, 5.00%, 10/01/54(a)		235		247,606
State of Connecticut, GO
Series 2021-A, 3.00%, 01/15/35		7,890		8,792,458
Series 2021-A, 3.00%, 01/15/40		5,000		5,477,400
				14,517,464
District of Columbia — 3.1%
Metropolitan Washington Airports Authority Refunding ARB, Series A, AMT, 5.00%, 10/01/40		3,410		4,408,312
Metropolitan Washington Airports Authority Refunding RB, Series A, AMT, 4.00%, 10/01/38		3,000		3,667,680
Washington Metropolitan Area Transit Authority, RB, Series A, 4.00%, 07/15/40		8,145		9,768,950
				17,844,942
Florida — 5.0%
Capital Trust Agency, Inc., RB, Series A, 5.00%, 06/01/45(a)		850		896,521
County of Lee Florida Airport Revenue, Refunding RB, Series A, AMT, 5.38%, 10/01/32		7,100		7,172,349
County of Miami-Dade Seaport Department, ARB
Series A, 5.38%, 10/01/33		3,145		3,497,334
Series B, AMT, 6.25%, 10/01/38		1,405		1,579,206
Series B, AMT, 6.00%, 10/01/42		1,885		2,114,555
Esplanade Lake Club Community Development District, SAB
Series A-1, 4.00%, 11/01/40		1,080		1,138,396
Series A-1, 4.13%, 11/01/50		385		403,342
Series A-2, 4.00%, 11/01/40		500		527,035
Series A-2, 4.13%, 11/01/50		500		523,820
Florida Development Finance Corp., RB(a)
AMT, 5.00%, 05/01/29		825		890,282
Series A, AMT, 5.00%, 08/01/29(b)		325		337,184
Florida Development Finance Corp., Refunding RB, Series C, 5.00%, 09/15/50(a)		475		520,196
Hillsborough County Aviation Authority, Refunding RB Series A, AMT, 5.25%, 10/01/30		3,255		3,605,596

1

Schedule of Investments  (unaudited) (continued) May 31, 2021 BlackRock MuniHoldings Investment Quality Fund (MFL) (Percentages shown are based on Net Assets)

Security	Par (000)		Value
Florida (continued)
Hillsborough County Aviation Authority, Refunding RB (continued)
Sub-Series A, AMT, 5.50%, 10/01/29	$	5,360	$	5,972,219
Lee County Housing Finance Authority, RB, S/F Housing, Series A-2, AMT, (FHLMC, FNMA, GNMA), 6.00%, 09/01/40		210		212,361
				29,390,396
Hawaii — 1.9%
State of Hawaii Airports System Revenue, ARB, Series A, AMT, 5.00%, 07/01/45		5,985		6,912,735
State of Hawaii Airports System Revenue, COP
AMT, 5.25%, 08/01/25		1,350		1,486,714
AMT, 5.25%, 08/01/26		2,500		2,752,175
				11,151,624
Idaho — 2.0%
Idaho Health Facilities Authority, RB, 4.00%, 12/01/43		10,000		11,535,400
Illinois — 17.0%
Chicago Board of Education, GO
Series A, 5.00%, 12/01/36		1,760		2,198,891
Series A, 5.00%, 12/01/38		715		888,781
Series A, 5.00%, 12/01/39		630		782,832
Series A, 5.00%, 12/01/40		1,285		1,587,553
Series A, 5.00%, 12/01/41		835		1,028,252
Chicago Board of Education, Refunding GO
Series A, 5.00%, 12/01/28		365		453,965
Series A, 5.00%, 12/01/29		440		554,044
Series A, 5.00%, 12/01/30		1,485		1,862,101
Chicago Board of Education, Refunding GO, CAB, Series A, 0.00%, 12/01/25(c)		395		367,453
Chicago Midway International Airport, Refunding ARB
Series A, 2nd Lien, AMT, 5.50%, 01/01/32		6,275		6,748,260
Series A, 2nd Lien, AMT, 5.00%, 01/01/41		8,020		8,821,038
Chicago Midway International Airport, Refunding RB, Series A, 2nd Lien, AMT, 5.50%, 01/01/30		6,500		6,994,845
Chicago O’Hare International Airport, ARB, Series D, Senior Lien, 5.25%, 01/01/42		2,630		3,227,457
Chicago O’Hare International Airport, Refunding RB
Series B, Senior Lien, 5.00%, 01/01/35		4,300		5,237,572
Series C, Senior Lien, 4.00%, 01/01/37		4,000		4,792,840
Series C, Senior Lien, 4.00%, 01/01/38		3,820		4,564,480
Series E, Senior Lien, (AGM), 4.00%, 01/01/39		5,000		5,927,650
Chicago Transit Authority Sales Tax Receipts Fund, RB, 5.25%, 12/01/21(d)		10,960		11,237,397
Illinois Finance Authority, RB, Series A, 6.00%, 08/15/41		4,000		4,048,560
Illinois State Toll Highway Authority, RB, Series A, 5.00%, 01/01/40		5,000		5,785,550
State of Illinois, GO
5.50%, 05/01/39		15,000		19,270,500
5.75%, 05/01/45		2,000		2,586,740
				98,966,761
Indiana — 0.5%
Indiana Finance Authority RB(e)
Series A, 5.00%, 06/01/41		550		607,453
Series A, 5.00%, 06/01/51		405		439,862

Security	Par (000)		Value
Indiana (continued)
Indiana Finance Authority RB(e) (continued)
Series A, 5.00%, 06/01/56	$	360	$	387,904
Indiana Finance Authority, RB, Series A, AMT, 5.00%, 07/01/40		1,240		1,333,459
				2,768,678
Massachusetts — 6.8%
Commonwealth of Massachusetts, GO, Series G, 4.00%, 09/01/42		20,000		22,982,000
Massachusetts Development Finance Agency, Refunding RB, 5.00%, 07/01/41		4,710		5,597,034
Massachusetts Educational Financing Authority, RB, AMT, 5.00%, 01/01/27		1,000		1,151,450
Massachusetts Housing Finance Agency, Refunding RB, M/F Housing, Series G, 3.45%, 12/01/30		3,100		3,376,582
Massachusetts School Building Authority, RB, Sub- Series B, 4.00%, 02/15/42		6,200		6,797,184
				39,904,250
Michigan — 2.0%
City of Detroit Michigan Water Supply System Revenue, RB, Series B, 2nd Lien, (AGM), 6.25%, 07/01/36		10		10,047
Michigan Finance Authority, RB, 4.00%, 02/15/44		10,000		11,535,700
				11,545,747
Mississippi — 2.5%
Mississippi Development Bank, RB
(AGM), 6.75%, 12/01/31		3,775		4,346,573
(AGM), 6.75%, 12/01/33		2,350		2,699,093
(AGM), 6.88%, 12/01/40		6,405		7,327,768
				14,373,434
New Jersey — 13.5%
New Jersey Economic Development Authority, RB
AMT, (AGM), 5.00%, 01/01/31		2,425		2,674,217
AMT, 5.38%, 01/01/43		7,000		7,742,280
New Jersey Economic Development Authority, Refunding RB, Series BBB, 5.50%, 06/15/30		4,080		5,041,656
New Jersey Health Care Facilities Financing Authority, Refunding RB, Series A, 5.00%, 07/01/43		5,000		6,005,650
New Jersey Higher Education Student Assistance Authority, Refunding RB, 1st Series, AMT, 5.75%, 12/01/28		1,590		1,626,491
New Jersey Transportation Trust Fund Authority, RB
Series AA, 5.50%, 06/15/39		8,175		8,947,129
Series AA, 4.00%, 06/15/40		4,000		4,637,160
Series AA, 5.00%, 06/15/45		3,250		4,038,872
Series BB, 5.00%, 06/15/44		5,000		6,027,050
Series S, 5.25%, 06/15/43		10,000		12,482,400
New Jersey Turnpike Authority, Refunding RB, Series A, 5.00%, 01/01/34		1,685		2,000,853
Tobacco Settlement Financing Corp., Refunding RB, Sub-Series B, 5.00%, 06/01/46		15,000		17,603,700
				78,827,458
New Mexico — 0.1%
City of Santa Fe New Mexico, RB, Series A, 5.00%, 05/15/39		310		348,350
New York — 12.4%
Hudson Yards Infrastructure Corp., RB, 5.75%, 02/15/47		7,510		7,545,973

SCHEDULE  OF  INVESTMENTS 2

Schedule of Investments  (unaudited) (continued) May 31, 2021 BlackRock MuniHoldings Investment Quality Fund (MFL) (Percentages shown are based on Net Assets)

Security	Par (000)		Value
New York (continued)
Metropolitan Transportation Authority, RB
Series A-1, 5.25%, 11/15/39.	$	7,005	$	7,700,947
Series C, 5.00%, 11/15/38		4,450		4,789,090
New York City Transitional Finance Authority Future Tax Secured Revenue, RB, Series C-3, Subordinate, 4.00%, 05/01/43		5,000		5,762,500
New York City Water & Sewer System, RB
Series BB, 5.00%, 06/15/49		11,865		15,091,568
Series CC-1, Subordinate, 5.00%, 06/15/51		5,635		7,329,895
New York Convention Center Development Corp., RB, CAB, Series B, Sub-Lien, (BAM-TCRS), 0.00%, 11/15/40(c)		7,000		4,370,660
New York Liberty Development Corp., Refunding RB, Series 1, Class 1, 5.00%, 11/15/44(a)		1,730		1,911,996
New York Power Authority, Refunding RB, Series A, 4.00%, 11/15/55		7,800		9,111,726
New York Transportation Development Corp., RB
AMT, 5.00%, 10/01/35		630		796,635
AMT, 5.00%, 10/01/40		1,775		2,213,638
Triborough Bridge & Tunnel Authority, Refunding RB, Series B, 5.00%, 11/15/38		4,400		5,435,276
				72,059,904
Ohio — 4.3%
Buckeye Tobacco Settlement Financing Authority, Refunding RB, Series B-2, Class 2, 5.00%, 06/01/55 .		8,490		9,826,920
Ohio Turnpike & Infrastructure Commission, RB
Series A-1, Junior Lien, 5.25%, 02/15/31		5,145		5,582,016
Series A-1, Junior Lien, 5.25%, 02/15/32		2,250		2,439,945
State of Ohio, RB, 4.00%, 01/01/41		6,000		7,064,160
State of Ohio, Refunding RB, Series A, 4.00%, 01/01/28(d)		25		30,241
				24,943,282
Pennsylvania — 5.7%
Bristol Township School District, GO, (SAW), 5.25%, 06/01/37		3,000		3,278,130
Bucks County Industrial Development Authority, RB 4.00%, 07/01/46		145		162,400
4.00%, 07/01/51		100		110,954
Pennsylvania Turnpike Commission, RB
Series A, 5.25%, 12/01/44		5,000		6,351,350
Sub-Series A, 5.50%, 12/01/46		18,570		23,025,129
				32,927,963
Puerto Rico — 4.6%
Puerto Rico Sales Tax Financing Corp. Sales Tax Revenue, RB
Series A-1, Restructured, 4.75%, 07/01/53		719		806,013
Series A-1, Restructured, 5.00%, 07/01/58		6,203		7,056,719
Series A-2, Restructured, 4.33%, 07/01/40		12,484		13,847,877
Series A-2, Restructured, 4.78%, 07/01/58		488		548,307
Series B-1, Restructured, 4.75%, 07/01/53		749		837,906
Series B-2, Restructured, 4.78%, 07/01/58		726		815,313
Puerto Rico Sales Tax Financing Corp. Sales Tax Revenue, RB, CAB, Series A-1, Restructured, 0.00%, 07/01/46(c)		8,018		2,600,398
				26,512,533
South Carolina — 5.4%
Charleston County Airport District, ARB
Series A, AMT, 5.25%, 07/01/25		4,490		4,939,494

Security	Par (000)		Value
South Carolina (continued)
Charleston County Airport District, ARB (continued)
Series A, AMT, 5.50%, 07/01/38	$	3,000	$	3,294,210
Series A, AMT, 6.00%, 07/01/38		5,270		5,841,162
Series A, AMT, 5.50%, 07/01/41		4,170		4,572,113
County of Charleston South Carolina, ARB, 5.25%, 12/01/38		6,735		7,515,048
South Carolina Jobs-Economic Development Authority, Refunding RB, Series A, 5.00%, 05/01/37		4,480		5,427,341
				31,589,368
Texas — 8.5%
City of Houston Texas Airport System Revenue, Refunding ARB, AMT, 5.00%, 07/15/27		410		480,176
City of Houston Texas Airport System Revenue, Refunding RB
Series A, AMT, 5.00%, 07/01/27		400		468,108
Series A, AMT, 6.63%, 07/15/38		700		704,522
Dallas Fort Worth International Airport, ARB, Series H, AMT, 5.00%, 11/01/21(d)		4,575		4,664,807
Lower Colorado River Authority, Refunding RB, 5.50%, 05/15/33		3,735		4,093,821
New Hope Cultural Education Facilities Finance Corp., RB, Series A, 5.00%, 08/15/50(a)		800		837,488
Red River Education Finance Corp., RB, 5.25%, 03/15/23(d)		7,170		7,813,077
State of Texas, GO, 5.00%, 04/01/43		15,550		18,421,152
Texas City Industrial Development Corp., RB, Series 2012, 4.13%, 12/01/45		445		480,498
Texas Water Development Board, RB 5.25%, 10/15/46		4,780		5,819,268
Series B, 4.00%, 10/15/43		5,000		5,891,250
				49,674,167
Utah — 2.4%
County of Utah, RB, Series B, 5.00%, 05/15/46		8,590		10,201,140
Utah Charter School Finance Authority, RB, Series A, 5.00%, 06/15/49(a)		320		338,800
Utah State University, RB, Series B, (AGM), 4.00%, 12/01/45		3,000		3,455,250
				13,995,190
Washington — 0.5%
State of Washington, GO, Series C, 5.00%, 02/01/41		2,500		3,109,925
Wisconsin(a) — 0.8%
Public Finance Authority, RB
Series A, 5.00%, 07/15/39		165		184,657
Series A, 5.00%, 07/15/49		630		691,242
Series A, 5.00%, 10/15/50		1,695		1,859,619
Series A, 5.00%, 07/15/54		300		326,937
Series A-1, 5.00%, 01/01/55		945		1,044,480
Public Finance Authority, Refunding RB, 5.00%, 09/01/49		520		532,126
				4,639,061
Total Municipal Bonds — 125.6%     (Cost: $676,051,227)			731,365,762

3

Schedule of Investments  (unaudited) (continued) May 31, 2021 BlackRock MuniHoldings Investment Quality Fund (MFL) (Percentages shown are based on Net Assets)

Security	Par (000)		Value
Municipal Bonds Transferred to Tender Option Bond Trusts(f)
Alabama — 8.2%
Alabama Special Care Facilities Financing Authority- Birmingham AL, Refunding RB, Series B, 5.00%, 11/15/46	$	39,718	$	47,758,129
Massachusetts — 4.4%
Commonwealth of Massachusetts, GO, Series E, 5.25%, 09/01/43		20,000		25,616,000
Michigan — 2.0%
Michigan Finance Authority, Refunding RB, Series A, 4.00%, 12/01/40		10,100		11,604,799
Nevada — 1.9%
County of Clark Nevada, GO, 4.00%, 07/01/47		10,000		11,310,900
New Jersey — 0.5%
New Jersey Transportation Trust Fund Authority, RB, Series B, 5.25%, 06/15/36(g)		2,961		2,970,151
New York — 16.3%
Hudson Yards Infrastructure Corp, Refunding RB, Series A, 4.00%, 02/15/44		30,165		33,835,464
New York City Transitional Finance Authority Building Aid Revenue, RB, Series S-1, 5.00%, 07/15/43		11,825		14,649,164
New York City Transitional Finance Authority Future Tax Secured Revenue, RB, Sub-Series B-1, 4.00%, 11/01/41		20,000		23,675,800
New York Liberty Development Corp., ARB, 5.25%, 12/15/43		13,950		14,313,695
New York Liberty Development Corp., Refunding RB, 5.75%, 11/15/51(g)		8,200		8,377,985
				94,852,108
Pennsylvania — 1.9%
Geisinger Authority, Refunding RB, Series A, 4.00%, 06/01/41		10,000		10,923,900
Total Municipal Bonds Transferred to Tender Option Bond Trusts — 35.2% (Cost: $190,230,956)				205,035,987
Total Long-Term Investments — 160.8% (Cost: $866,282,183)				936,401,749

Security	Shares		Value
Short-Term Securities
Money Market Funds — 0.4%
BlackRock Liquidity Funds, MuniCash, Institutional Class, 0.01%(h)(i)		2,412,363	$	2,412,845
Total Short-Term Securities — 0.4% (Cost: $2,412,801)				2,412,845
Total Investments — 161.2% (Cost: $868,694,984)				938,814,594
Other Assets Less Liabilities — 1.6%				9,386,962
Liability for TOB Trust Certificates, Including Interest Expense and Fees Payable — (15.7)%				(91,558,193	)
VRDP Shares at Liquidation Value, Net of Deferred Offering Costs — (47.1)%				(274,260,626	)
Net Assets Applicable to Common Shares — 100.0%			$	582,382,737

^(a)  Security exempt from registration pursuant to Rule 144A under the Securities Act of 1933, as amended. These securities may be resold in transactions exempt from registration to qualified institutional investors.

^(b) Variable rate security. Interest rate resets periodically. The rate shown is the effective interest rate as of period end. Security description also includes the reference rate and spread if published and available.

^(c) Zero-coupon bond.

^(d) U.S. Government securities held in escrow, are used to pay interest on this security as well as to retire the bond in full at the date indicated, typically at a premium to par.

^(e) When-issued security.

^(f) Represent bonds transferred to a TOB Trust in exchange of cash and residual certificates received by the Trust. These bonds serve as collateral in a secured borrowing.

^(g) All or a portion of the security is subject to a recourse agreement. The aggregate maximum potential amount the Trust could ultimately be required to pay under the agreements, which expire between June 15, 2036 to November 15, 2051, is $6,643,355.

^(h) Affiliate of the Trust.

⁽ⁱ⁾  Annualized 7-day yield as of period end.

Affiliates

Investments in issuers considered to be affiliate(s) of the Trust during the period ended May 31, 2021 for purposes of Section 2(a)(3) of the Investment Company Act of 1940, as amended, were as follows:

Affiliated Issuer	Value at 08/31/20		Purchases at Cost		Proceeds from Sales			Net Realized Gain (Loss)		Change in Unrealized Appreciation (Depreciation)		Value at 05/31/21		Shares Held at 05/31/21		Income		Capital Gain Distributions from Underlying Funds
BlackRock Liquidity Funds, MuniCash, Institutional Class	$	17,313,007	$	—	$	(14,900,587	)(a)	$	381	$	44	$	2,412,845		2,412,363	$	569	$	—

^(a) Represents net amount purchased (sold).

SCHEDULE   OF   INVESTMENTS 4

Schedule of Investments  (unaudited) (continued) May 31, 2021 BlackRock MuniHoldings Investment Quality Fund (MFL)

Derivative Financial Instruments Outstanding as of Period End

Futures Contracts

Description	Number of Contracts		Expiration Date		Notional Amount (000)		Value/ Unrealized Appreciation (Depreciation)
Short Contracts
10-Year U.S. Treasury Notes		326		09/21/21	$	42,971	$	(20,939	)
U.S. Long Bond		141		09/21/21		22,018		(68,502	)
							$	(89,441	)

Fair Value Hierarchy as of Period End

Various inputs are used in determining the fair value of financial instruments. These inputs to valuation techniques are categorized into a fair value hierarchy consisting of three broad levels for financial reporting purposes as follows:

• Level  1 – Unadjusted price quotations in active markets/exchanges for identical assets or liabilities that the Trust has the ability to access;

• Level  2 – Other observable inputs (including, but not limited to, quoted prices for similar assets or liabilities in markets that are active, quoted prices for identical or similar assets or liabilities in markets that are not active, inputs other than quoted prices that are observable for the assets or liabilities (such as interest rates, yield curves, volatilities, prepayment speeds, loss severities, credit risks and default rates) or other market–corroborated inputs); and

• Level  3 – Unobservable inputs based on the best information available in the circumstances, to the extent observable inputs are not available (including the BlackRock Global Valuation Methodologies Committee’s (the “Global Valuation Committee’s”) assumptions used in determining the fair value of financial instruments).

The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). Accordingly, the degree of judgment exercised in determining fair value is greatest for instruments categorized in Level 3. The inputs used to measure fair value may fall into different levels of the fair value hierarchy. In such cases, for disclosure purposes, the fair value hierarchy classification is determined based on the lowest level input that is significant to the fair value measurement in its entirety. Investments classified within Level 3 have significant unobservable inputs used by the Global Valuation Committee in determining the price for Fair Valued Investments. Level 3 investments include equity or debt issued by privately held companies or funds. There may not be a secondary market, and/or there are a limited number of investors. The categorization of a value determined for financial instruments is based on the pricing transparency of the financial instruments and is not necessarily an indication of the risks associated with investing in those securities. For information about the Trust’s policy regarding valuation of financial instruments, refer to its most recent financial statements.

The following table summarizes the Trust’s financial instruments categorized in the fair value hierarchy. The breakdown of the Trust’s financial instruments into major categories is disclosed in the Schedule of Investments above.

	Level 1			Level 2		Level 3		Total
Assets
Investments
Long-Term Investments
Municipal Bonds	$	—		$	731,365,762	$	—	$	731,365,762
Municipal Bonds Transferred to Tender Option Bond Trusts.		—			205,035,987		—		205,035,987
Short-Term Securities
Money Market Funds		2,412,845			—		—		2,412,845
	$	2,412,845		$	936,401,749	$	—	$	938,814,594
Derivative Financial Instruments(a)
Liabilities
Interest Rate Contracts.	$	(89,441	)	$	—	$	—	$	(89,441)

^(a) Derivative financial instruments are futures contracts. Futures contracts are valued at the unrealized appreciation (depreciation) on the instrument.

The Trust may hold assets and/or liabilities in which the fair value approximates the carrying amount for financial reporting purposes. As of period end, such assets and/or liabilities are categorized within the fair value hierarchy as follows:

	Level 1		Level 2			Level 3		Total
Liabilities
TOB Trust Certificates	$	—	$	(91,534,330	)	$	—	$	(91,534,330	)
VRDP Shares at Liquidation Value		—		(274,600,000	)		—		(274,600,000	)
	$	—	$	(366,134,330	)	$	—	$	(366,134,330	)

5

Schedule of Investments  (unaudited) (continued) May 31, 2021 BlackRock MuniHoldings Investment Quality Fund (MFL)

Portfolio Abbreviation
AGC-ICC	Assured Guaranty Corp. – Insured Custody Certificate
AGM	Assured Guaranty Municipal Corp.
AMT	Alternative Minimum Tax
ARB	Airport Revenue Bonds
BAM-TCRS	Build America Mutual Assurance Co.- Transferable Custodial Receipts
CAB	Capital Appreciation Bonds
COP	Certificates of Participation
FHLMC	Federal Home Loan Mortgage Corp.
FNMA	Federal National Mortgage Association
GNMA	Government National Mortgage Association
GO	General Obligation Bonds
M/F	Multi-Family
RB	Revenue Bond
S/F	Single-Family
SAB	Special Assessment Bonds
SAW	State Aid Withholding

SCHEDULE   OF   INVESTMENTS 6