They have something common. Both of them are good dancing. A. in; onB. in ; atC. at ; onD.

问题补充：

They have something common. Both of them are good dancing.

A. in; on

B. in ; at

C. at ; on

D. at ; at

答案：

A. in; on

(答案→)B. in ; at

C. at ; on

D. at ; at

解析：句意：他们有某些共同点。他们两个都擅长跳舞。in common相同；be good at擅长……。根据介词的宾语，然后根据上面这两个短语判断答案。