The two girls are so alike that strangers finddifficult to tell one from the other.A. itB.

问题补充：

The two girls are so alike that strangers finddifficult to tell one from the other.

A. it

B. them

C. her

D. that

答案：

(答案→)A. it

B. them

C. her

D. that

解析：句意：这两个女孩是如此的相似,以至于陌生人很难区分他们。it 是形式宾语，to tell one from the other是真正的宾语。故选A。