22. (1) used to do 表示“过去常常做某事”
如：I used to get up at 6 o'clock. But now I often get up at 7 . 我过去常常6点起床。但现在我经常7点起床。
My grandmother used to be a history teacher in a middle school. 我祖母曾经是中学的历史老师。
(2) be used to doing sth. 表示“习惯于做某事”
如：We are used to reading English very early in the morning. 我们习惯于早上很早读英语。
Are you used to living in Beijing now? 你现在习惯住在北京了吗？
(3) be used to do/be used for(doing) 表示被“被用来做某事”，主语常常是物。
A knife is used to cut something. 小刀是用来切东西的。
Mobile phones are used to communicate with other people. 手机是用来与其他人通讯的。
23. wait for sth.的意思是“对……急不可待”；
 wait to do sth.的意思是“等不及做……”。
如：The children  wait for the Christmas Party. 孩子们对圣诞聚会迫不及待。
24. think of 想起， 记起， 想出
think about 思考， 考虑；
think over 仔细考虑。
如：They think of a wonderful idea.
他们想出了一个好主意。
We are thinking about when to go to Paris.
他们在考虑什么时候去巴黎。
Think it over，you can solve this problem very soon.
仔细思考，你将会很快解决这个问题。
25. have to, must
have to 往往是客观外界情况造成 “不得不”，
must 表示说话人主观上认为 “应该” “有必要”。
如：It is late now. We have to leave, or we will be late. 现在很迟了。我们不得不离开了，不然我们就要迟到了。
I must finish my task this afternoon. 我必须今天下午完成任务。