Students mustn't smoke or drink while＿＿ at school.A.studyB.studyingC.to studyD.studied
问题描述：
Students mustn't smoke or drink while＿＿ at school.
A.study
B.studying
C.to study
D.studied
答
B
while后面只能加进行时
而且此句是一个省略
应该是 Students mustn't smoke or drink while they are studying at school.