Question

The old man has four sons, and two _____ turned doctors．

A．of which

B．of whom

C．of them

D．of that

Answer 1

C

考查定语从句。句中有逗号，不小心会误以为是非限制性定语从句，但and连接前后两分句，故不是定语从句。“其中的两个”是two of them。故选C。