问题
选择题
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
答案
答案：C
考查倒装结构。句中主语从句用only + 状语从句 + 倒装结构，根据句意选C。