Listening to loud music at rock concerts caused hearing loss in some teenagers.A. isB. a

问题补充：

Listening to loud music at rock concerts caused hearing loss in some teenagers.

A. is

B. are

C. has

D. have

答案：

A. is

B. are

(答案→)C. has

D. have

解析：在摇滚音乐会听大声音乐在一些青少年中已经引起了听力的损伤。动名词作主语谓语动词用单数，已经引起，应为完成时。