他过去学习不努力。当老师上课时，他假装在认真听讲。(used to，when)He used not to work hardWhen the teacher had class

他过去学习不努力。当老师上课时，他假装在认真听讲。(used to，when)
He used not to work hard．When the teacher had class，he pretended to listen to the teacher carefully．

(答案→)He used not to work hard．When the teacher had class，he pretended to listen to the teacher carefully． 解析：表示过去习惯于做某事可用used to+动词原形，否定形式可以写成used not to do，所以本题的第一句可翻译成He used not to work hard。本题的第二句含有时间状语从句，可以用when来引导，本题描述的是过去，要用过去时，故老师上课可以翻译成the teacher had class，假装做某事可翻译pretend to do，听课可以翻译成listen to the teacher，修饰动词听应该用副词carefully，故本题的第二句可翻译成When the teacher had class，he pretended to listen to the teacher carefully。

和我的回答一样，看来我也对了