—Were you at home at 9:00 last night? I called you but nobody answered. —Sorry I at that

问题补充：

—Were you at home at 9:00 last night? I called you but nobody answered.

—Sorry, I at that time.

A. take a shower

B. took a shower

C. was taking a shower

D. am taking a shower

答案：

A. take a shower

B. took a shower

(答案→)C. was taking a shower

D. am taking a shower

解析：句意：昨晚九点钟你在家吗啊？我给你打电话了，但是没有人接。——抱歉，那个时侯我正在洗澡。结合语境可知下文描述的是过去某时正在进行的动作，故用过去进行时态，选C。