21.【2020•长沙市】The twins are so alike that even their father finds________ hard to tell them from each other.
A. it B. him C. them
【答案】A
【解析】句意：这对双胞胎如此相像以至于甚至他们的父亲都发现很难区分他们。考查代词辨析。it它；him他，人称代词宾格形式；them他们，人称代词宾格形式。根据句意和句子结构可知，这里使用了句型find it+形容词+to do sth.“发现做某事是……的”，it是形式宾语，动词不定式是真正的宾语。故选A。