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be used to do sth：
use有使用，用的意思，use sth. to do sth. 表示用什么来做什么，be used 是 used 的被动形式，所以 be used to do sth. 表示某物被用来做某事，这里的to后面要加动词原形。
如:
The candle in the box can be used to lighten the dark room.
盒子里的蜡烛可以用来照亮这个黑暗的房间。
Retaining walls stabilize a slope and protect planted areas from erosion, but they can be used to do much more.
护土墙斜坡稳定和保护免受侵蚀的种植区，但它们可以用来做更多的工作。
Tip: This method can be used to upload the contents of a file to a server.
提示：这个方法的作用是：将一个文件的内容上传到一个服务器中。
The land is useful for the man. Because it can be used to do mortgages.
这块土地对这个人来说有很大用处，因为它可以用来做抵押贷款。
be used to sth./doing......
表习惯于某事或者习惯于做某事，此处to为介词，其后要加V-ing形式。
如：He is an experienced driver and he is used to driving
in all kinds of weather.
他是一位有经验的驾驶员，他习惯于在各种各样的天气情况下开车。
We are used to the noise from the traffic now.
我们现在已经习惯了交通的嘈杂声。
That must be especially hard in an environment that is so used to doing everything in a way that has already be done.
在 一个一切都习惯于去循规蹈矩的环境里，这样做一定很艰难。
used to do sth.
表示过去常常做某事，to为不定式符号，其后要加动词原形。
如：
I used to run around and play, and I used to do it every day.
我常常到处跑并且玩, 我过去常常每天做它。
I found Marian and Laura sitting comfortably together in the small sitting room where I used to do my work.
我找到麦闰和瑙若，舒服坐在一起，就是那间我用来工作过的小房间。
I used to do it more years ago, but not so much now my sons are grown up and away.
我很多年前就开始了，但现在不常做了，我儿子也大了离家出去闯荡了。
注意：
1. used to do 既不能与表示具体次数的词或者短语连用（once,twice,three times等），也不能和表示一段时间的词或者短语连用（one month.two years等）。
如：
I used to brush my teeth three times a day. 错误
I brushed my teeth three times a day before. 正确
我以前经常一天刷牙三次。
They used to live in Paris for five years.错误
They live in Paris for five years. 正确
他们在法国生活了五年。
2. 虽然used to do 本身含有“经常”，“ 常常” 的意思，但是它仍然可以与表示频率的副词sometimes,always,often,never等连用。
如：
He often used to do his homework on Sunday, but now he does homework on Saturday.
他过去常在星期天做家庭作业，但是现在他在星期六做作业。
He always used to do all the housework by himself because he has no wife.
他过去总是一个人把所有的家务活都干了,因为他没有老婆。
3. used to do 的否定形式和疑问形式：
借助助动词 didn't, 变为didn't use to do 或者直接使用usedn't。
如：
We didn't use to do that with him so often.
/ We usedn't to do that with him so often.
我们不太习惯经常和他在一起了。
They used to come here, didn't they?
/They used to come here, usedn't they?
他们以前经常来这里， 对吗？
单词卡片（创金经英语原创）
创金经英语原创
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