At the age of fifteen she gave up taking piano lessons to her school work.A. hold onB. ca

问题补充：

At the age of fifteen she gave up taking piano lessons to her school work.

A. hold on

B. call on

C. put on

D. concentrate on

答案：

A. hold on

B. call on

C. put on

(答案→)D. concentrate on

解析：句意，在十五岁时，她放弃了上钢琴课，专心于她的学校功课。hold on坚持 call on 号召 put on穿上 concentrate on专心于，根据题意，故选D。