By the time of last year she the piano for five years.A. learntB. has learntC. had learn

问题补充：

By the time of last year, she the piano for five years.

A. learnt

B. has learnt

C. had learnt

D. will learn

答案：

A. learnt

B. has learnt

(答案→)C. had learnt

D. will learn

解析：句意：到去年为止，她已经学习钢琴五年了。结合语境可知本描述的是一直持续到去年的动作，故用过去完成时态，选C。