问一个GMAT句子改错

题目

问一个GMAT句子改错
The lack of complete historical records from the mid-to-late 1800's has made it difficult in tracing some Black inventions to their originators.
正确答案是把in tracing改成to trace
给出的原因解释是 作为形式宾语的代词it,不能向后指代介词短语in tracing 而可以向后指代不定时短语to trace
尤其是形式宾语的向后指代问题

答案

difficult in doing/to do 都可以make sth./sb.sth./adj.这里是 make it adj.;楼上讲的不完全对,不是考make it to do/ in doing.GMAT选择顺序：实意名词〉动词〉形容词〉抽象名词〉分词动名词〉从句代词it作为形式主...