Canhavedone的用法与理解
can have done 是什么意思 用于什么情况??? -
can have done 通常只用于疑问句和否定句；用于疑问句时表怀疑，用于否定句时表不确定。例如：Can they have left so soon?难道他们这么快就走了？（表怀疑）He can’t have been to that town.他不可能去过那座城市。（表不确定）lt;><><> could have done 可用于肯定句、疑问句和否定句；用于好了吧！
1.can+have+done表示对过去行为的怀疑，用于疑问句，译成“可能做过……吗？“2.could+have+done是虚拟语气，表示对过去事情的假设，意思是本来能够做某事而没有做。3.could (不能用can) have done “表示“过去本能够做某事却未做。”注意：其否定形式couldn't have done 没有虚拟语气的用法。4还有呢？
can have done 通常只用于疑问句和否定句；用于疑问句时表怀疑，用于否定句时表不确定。例如：Can they have left so soon?难道他们这么快就走了？（表怀疑）He can’t have been to that town.他不可能去过那座城市。（表不确定）lt;><><> could have done 可用于肯定句、疑问句和否定句；用于好了吧！
1.can+have+done表示对过去行为的怀疑，用于疑问句，译成“可能做过……吗？“2.could+have+done是虚拟语气，表示对过去事情的假设，意思是本来能够做某事而没有做。3.could (不能用can) have done “表示“过去本能够做某事却未做。”注意：其否定形式couldn't have done 没有虚拟语气的用法。4还有呢？
用于疑问句和否定句，when还有呢？can+代词have done表：什么时候谁可以怎样How can I repair the wrong I have done her?我怎样才能补偿对她做过的错事呢Where can I have my laundry done?脏衣服送到哪里去洗？Upon self-examination, I can flatter myself that I have done no wrong自问没还有呢？
1、can have done 和could have done 的区别can have done是表示应该做某事而没有做，所以既然知道没有做，那肯定是已经发生了。could have done 表示本能做而实际未做，是虚拟语气.2、can't have done和couldn't have done的区别can't have done（不可能做过）是must have done（一定做过）的还有呢？
must have done ,can have done -
must have done 一定做过某事(表示对过去发生的事的肯定推测)can have done 可能做过某事(表示对过去发生的事的不确定的推测)如：He must have been there yesterday.他昨天肯定去过那儿。He can have been there yesterday.他昨天可能去过那儿。
He can't have taken it home.他不可能把它带回家了。（表不可能）could have done could have done 可用于肯定句、疑问句和否定句。用于肯定句既可以表示过去能够做而实际未做，有惋惜、遗憾或委婉批评之意，也可以表示对过去动作的推测；用于否定句和疑问句的情况与can have done相同。例如：You 后面会介绍。
could have done 和 can have done 有什么区别?还有would have done...
“can+have+done”表示对过去行为的怀疑，用于疑问句，译成“可能做过……吗？“could+have+done”是虚拟语气，表示对过去事情的假设，意思是本来能够做某事而没有做。“would+have+done”虚拟语气，表示对过去事情的假设，意思是“本来会做”。
- "can't have done"的字面意思是“不可能已经做过某事”，它表示主观上持有不可能或不太可能某种行为或事件已经发生的观点。 "couldn't have done"的字面意思是“不可能已经做过某事”，它强调过去发生的某事已经不可能发生。例句： I can't have left my keys at home. I remember putting 等我继续说。
can have done和 could have done有什么区别? -
could 委婉一些，更常用一些could have done 还表示虚拟语气，与过去事实相反can have done 表示对过去某事的推测，“可能已经做某事”
can have done \ could have done 用于表示对过去发生的事进行猜测，CAN 只能用于疑问句，否定句，其他情况用COULD,例如WHERE CAN SHE HAVE GONE? SHE CAN HARDLY HAVE GONE TO CHURCH.SHE COULD /MIGHT/MAY HAVE GONE SWIMMING.could have done 还可以1,表示某事本来可能发生而没有发生.例如WHY DID 是什么。