D. Washington, D.C
Explanation:
The United States Congress abolished the slave trade in the D.C on September 20, 1850, as part of the Compromise of 1850.
The answer is D-
Washington D.C
a historian researching the immigration policies of the early 1900s would expect a source written today,rather than in 1910 to :
( a ) be more interested in objective data and statistics.
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