大全sec11-11 it指代

napoleon8424

The lack of complete historical records from the mid-to-late 1800's have made some Black inventions difficult to trace to their originators.
(A)have made some Black inventions difficult to trace to their originators.
(B)have made for difficulties in tracing some inventions by Blacksto their originators.
(C)have made it difficult to trace someinventions by Blacks to their originators.
(D)has made it difficult to trace someinventions to their Blacks originators.
(E)has made it difficult in tracing someBlacks inventions to their originators.

答案D
made it那个it指代什么？
gmat可以形式宾语么？

napoleon8424

谢谢噢~看来Gmat允许形式宾语

liexodus

指代to trace someinventions to their Blacks originators
当然可以吖~