The old man has four sons and two turned doctorsA. of whichB. of whomC. of themD. of th

问题补充：

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

A. of which

B. of whom

C. of them

D. of that

答案：

A. of which

B. of whom

(答案→)C. of them

D. of that

解析：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。