Mary can speak Chinese fluently impressed me most.A. whyB. thatC. whereD. which

问题补充：

Mary can speak Chinese fluently, impressed me most.

A. why

B. that

C. where

D. which

答案：

A. why

B. that

C. where

(答案→)D. which

解析：which在句中引导非限定性定语从句。