Need 作为情态动词时，不要用于肯定句中。

 她该独立完成家庭作业。 She needs to do her homework by herself

 情态动词+ have done

May have done， might have done， 表示“大概已经” 通常用于肯定句和否定句。

 might 有时可用于疑问句。

Can have done,    could have done, 表示“可能已经”通常用于疑问句和否定句。

 could 有时可用于肯定句。

must have done, 表示“一定已经”只用于肯定句，具有较大的可能性

 should have done, 表示“本该” 可能性较小，表示对过去发生的动作的遗憾或责备

might have done, 表示本可以，通常用于肯定句

could have done, 表示本可以，通常用于肯定句。

should have done, 表示应该，可用于肯定句、否定句和疑问句。

 ought to have done, 表示“应该” 同 should have done, 。

needn't have done, 表示“本没有必要”只用于否定句。

表示对过去事实不大肯定的推测，常译为“可能已经”。may have done,  

 might have done

 也许他们乘坐的是晚一点儿的火车。They might have taken a later train

 他似乎对那个城市很熟悉，他以前可能去过那儿。He seems to know the city quite well,  He may have been there before

 表示“本来应该或可以做但没有做某事”，含有轻微的责备口吻或遗憾。

 你本来应该给他更多的帮助，虽然你很忙。You might have given him more help,  though you were busy

 这个建议本该拒绝的。The proposal might have been refused

 表示对过去事实的推测，常用于否定句和疑问句。Can have done,  could have done

 昨天他不可能看电视，因为他知道快要考试了。He can't couldn't have watched TV yesterday for he knew they would have an exam

 我不知道昨天她为什么没给我打电话，难道她会把我的电话号码忘了吗？I don't know why she didn't call me yesterday,  Can she have forgotten my telephone number?  

  I don't know why she didn't call me yesterday,  Could she have forgotten my telephone number?

 他昨天没来学校，难道他生病了？He didn't come to school yesterday, Can he have been ill?

 could 可表示对过去能做而未做的事感到惋惜、遗憾，可译成“本来是可以的”。

 为什么索菲不申请这项工作？她本来是能得到的。Why didn't Sophie apply for the job？ She could have got it

 你到纽约时为什么住宾馆？你完全可以和芭芭拉住在一起的。Why did you stay at a hotel when you went to New York？ You could have stayed with Barbara

 如果给我们更多的时间，我们完全可以把这项工作干得更好。Given more time， we could have done the work better

 must have done 表示对过去事实有把握的推测，具有较大的可能性。只用于肯定句中，

否定句和疑问句用 can have done，   could have done 。

 他的表肯定停了。His watch must have stopped

 昨天我给你家打电话，一位男士接了电话，但我没听出来是谁的声音。 I rang your flat yesterday,   a man answered but I didn't recognize the voice

 哦，那一定是我哥哥彼得。 Oh , it must have been my brother Peter

 用于虚拟语气中时，表示与过去事实相反。

 如果你早一点儿起床的话，你准能赶上那一班公共汽车了。You must have caught the bus， if you had got up earlier

 如果他足够细心的话，他准能赢得比赛。 He must have won the game， if he had been careful enough

 needn't have done用于对过去的责备，表示“没有必要做某事，可是做了”。

 机场离这儿很近，你没必要早早地赶到那里。The airport is close to us,  You needn't have hurried there early

 他还小，你没必要送他这么昂贵的礼物。He is still young,  You needn't have sent him such an expensive present

如表示“过去不必做也没有做”之意，需用 didn't need to do 。

 今天天气不冷，我没有必要把厚毛衣拿出来。（实际上也没拿）it is not cold today, I didn't need to take the thick sweaters out

表示对过去动作的责备或批评。should have done

 ought to have done

你们应把功课复习好的。You should have gone over your lessons

 事实上你们没有把功课复习好。in fact you didn't go over your lessons

你们昨天晚上本不该看电视。You shouldn't have watched TV last night

 事实上昨天晚上你们看了电视。 in fact you watched TV last night

 没有经过允许，你们本不该进老师的办公室。You oughtn't to have entered the teachers' office without permission

 你不该独自去那荒凉之地。You oughtn't to have gone to the deserted place alone

 如果航班准点的话，你今早就能到上海了。If the flight was on time you should have arrived in Shanghai early this morning       

 If the flight was on time you ought to have arrived in Shanghai early this morning

 这幢建筑物本周末前应该能完工。The building should have been completed by the end of the week       

The building ought to have been completed by the end of the week