1. 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 Blacks to their originators
(C) have made it difficult to trace some inventions by Blacks to their originators
(D) has made it difficult to trace some inventions to their Black originators（D）
(E) has made it difficult in tracing some Black inventions to their originators
偶认为是difficulty in doing sth.解释上是说make it adj to do， 我不知道要遵照哪个词组，大家帮帮忙啊 | 
