The engineer my father works is about 50 years old. A. to whom B. on whom C. with which D.

问题补充：

The engineer my father works is about 50 years old.

A. to whom

B. on whom

C. with which

D. with whom

答案：

A. to whom

B. on whom

C. with which

(答案→)D. with whom

解析：with whom引导定语从句.with whom放在从句中即为:my father works with the engineer.