.—? —I usually play tennis.A. Why do you play tennisB. What do you usually do on weekendsC

问题补充：

.—? —I usually play tennis.

A. Why do you play tennis

B. What do you usually do on weekends

C. When do you play tennis

D. Where do you play tennis

答案：

A. Why do you play tennis

(答案→)B. What do you usually do on weekends

C. When do you play tennis

D. Where do you play tennis

解析：句意：——你经常在周末做什么？——我经常打排球。根据—I usually play tennis可知此处询问做些什么。故选B。