It was announced that only when the examination papers were handed in ________to go out of the classroom．
A.the students would be permitted
B.had the students been permitted
C.would the students be permitted
D.the students had been permitted
网友回答
C解析考查倒装结构。句中主语从句中only + 状语 + 倒装结构，根据时态，选C。