May I go now?- No. You let the teacher know first.”A. need B. must C. canD. may

问题补充：

--- May I go now?

--- No. You let the teacher know first.”

A. need

B. must

C. can

D. may

答案：

A. need

(答案→)B. must

C. can

D. may

解析：根据上文的问句内容，可知需要用情态动词，must，故选答案为B