Unless to answer questions, the pupils won't talk in Mrs Smith's class.
A. asking
B. asked
C. being asked
D. having asked
网友回答
A. asking
(答案→)B. asked
C. being asked
D. having asked
解析：B 连词省略句。该句中的unless引导的条件状语从句的主语是the pupils，与主句的主语相同，the pupils与ask之间是被动关系，应该使用过去分词的形式。故B正确。