问题补充：
--- Do you know ?
--- Next Sunday.
A. what they will do
B. what will they do
C. when will they come
D. when they will come
答案：
A. what they will do
B. what will they do
C. when will they come
(答案→)D. when they will come
解析：宾语从句。根据答语可知提问时间用特殊疑问词when；根据语序故选D。
