Ju Hua Tai is a popular song among young people were often heard singing it in Karaoke.A.

问题补充：

Ju Hua Tai is a popular song among young people, were often heard singing it in Karaoke.

A. which

B. who

C. that

D. what

答案：

A. which

(答案→)B. who

C. that

D. what

解析：考察定语从句。一旦判定为定语从句，就应该排除what ,又因为非限定性，所以排除that .因为先行词是young people 所以选who.