e used to do sth .
被动语态,被用来做某事.
Eg：The knife is used to cut.
to do sth是动词不定式引导的目的状语,修饰 be used.
如果后面不接状语,不定式就可以省略了哦!
另外,延伸两个词组.
1.be used to doing sth.
习惯做某事.
I'm not used to doing shopping online.
我不习惯于网上购物.
You'll get used to it.
你会习惯的.
2.used to do sth.
过去常常做某事.过去一向,过去时常;过去曾(而现在不再)做
He used to celebrate his birthday with Mary.
他过去常常与Mary一起庆祝他的生日.（暗示现在不了）
有问题直接call我哦,我在线~