He has a friend who the piano very well .A. playB. playingC. playsD. played

问题补充：

He has a friend who the piano very well .

A. play

B. playing

C. plays

D. played

答案：

A. play

B. playing

(答案→)C. plays

D. played

解析：句意：他有个朋友，钢琴弹得很好。句中who引导定语从句，修饰先行词friend；who指代的是a friend,是第三人称单数，所以从句中谓语动词用第三人称单数形式，故选C。