My mother when I got home.A. cookB. cookingC. was cookingD. cooks

问题补充：

My mother when I got home.

A. cook

B. cooking

C. was cooking

D. cooks

答案：

A. cook

B. cooking

(答案→)C. was cooking

D. cooks

解析：句意：当我到家时，我母亲正在做饭。根据时间状语从句when I got home.可知这是过去时，因此此处过去进行时。故选C。