After the discussion the students asked their teacher next. A. which to doB. what to do

问题补充：

After the discussion, the students asked their teacher next.

A. which to do

B. what to do

C. how to do

D. when to do

答案：

A. which to do

(答案→)B. what to do

C. how to do

D. when to do

解析：动词不定式和疑问代词或副词连用充当句子的某个成分。经过一番讨论，学生们问老师下步该怎样做。