A good friend of mine fromI was born showed up at my home rightbefore I left for Beijing．A

问题补充：

A good friend of mine from

I was born showed up at my home right

before I left for Beijing．

A. how

B. whom

C. when

D. which

答案：

A. how

B. whom

(答案→)C. when

D. which

解析：宾语从句。从句中缺少状语。