Can与be able to用法
Can与be able to用法
一．Can 与 be able to 译 “能/会”，两者后跟v原，即 can+v原， be able to +v原。具体can的过去式
地说，can不随主语人称/数的变化而变化，只用于一般现在时和一般过去式，can过去式 could；be able to 随主语人称/数和时态变化而变化，且可用于各个时态。Can于be able to在一般现在时、一般过去式相等，即can=am/is/are able to,could = was/were able to.
二、 be able to 在各个时态的结构与can /could 之间的关系
1、 一般现在时：am/is/are able to +v原=can +v原
1.）I'm able to (can) learn it on my own .我能自己学会它。
2.）They're able to (can) arrive there on time.他们能准时到哪儿。
2、 一般过去时：was/were able to +v原=could+v原。eg.
1.)He was able to run fast six years ago.六年前他能够跑得很快。
2.）We were able to write well them.那时我们能够写好。
3、 一般将来时：will be able to+v原（不等于）can +v原，其否定式 won't be able to+v原.eg
  My aunt will be able to go to hainan next week.
  变否定式：My aunt ______  ______ _______  ______ go to hainan next week.
4、 现在完成时：have（has） been able to +v原（不等于）can/could +v原.变否定式 haven't(hasn't) been able to +v原
  1.) His parent have been able to promise him to have a rest .他的父母亲已能答应他休息一会儿。
三、含can 的句子完成反义疑问句仍用can完成；含be able to 的句子用be的适当形式完成，而含will be able to 的句子用will 的确定式完成。Eg.
1.I can speak English,______  _____?
2.He is able to speak Japanese,_______  _____?
3.They are able to do it ,_____ _____?
4.We were able to reach there ,_____  ______?
5.My little sister was able to ride a bike,_______  ______?
6.His uncle won't be able to learn English,_______  _______?
7.My aunt will be able to finish the work,________  _______?

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