【1】  
You mustn't speak to your mother like that, ___you?
A.should
B.must
C.may
D.dare
                    

【2】
He was often listened ___in the next room.
A. sing
B.sung
C.to sing
D.to to sing


【3】
By the time the new pupil ___enough courage to raise his hand, the bell for the end of the lesson___.
A.had gathered   ;    was already rung
B.was gathering  ;    had already rung
C.gathered         ;    already rang
D.would gather   ;    would already have

回复 3# snowmother

   
第二题的答案是D的说。
我开始选的和你一样的、
listen to 是一个词组，是不是应该看成一个整体呢？  be seen to do something   把seen 换成listened to？？？？

回复 4# snowmother


  By the time 引到的时间状语从句中，不一定用过去完成时吧！？
我觉得关键看那个动作先发生，那个动作后发生，
如：By the time he got to the station, the train had gone.

但是你的例句让我更加理解了表达的句意~~谢谢！

C
be listened to 是被动语态，原型为 listen to sb do sth
类似的感官动词如see,hear，listen to 后面都接动词原形