情态动词的现在完成式的用法你知道么？还不快来看看？

情态动词现在完成式关键有两个作用：表明早已产生的情形和表明虚拟语气。在这里2个层面must/mustn’t；

can/can’t；need/needn’t；may/mayn’t；might/mightn’t；should/shouldn’t；

ought等情态动词＋进行式表示的意思是有一定差别的。

1.表明早已产生的状况。

1）must have 过去分词，表明对已产生状况的毫无疑问推断，译为“（昨日）一定……”。如：

My pain__________ apparent the moment I walked into the room， for the first man I met askedsympathetically：“Are you feeling all right？”

[A] must be[B] had been [C] must have been [D] had to be

（回答为C）

2）can’t / couldn’t have 过去分词，表明对已产生状况的否认推断，译为“（昨日）一定没……”。如：

Mary__________ my letter；otherwise she would have replied before now.

[A] couldn’thave received [B] ought to have received

[C] hasreceived [D] shouldn’t have received

（回答为A）

3）may / might have 过去分词，表明对已产生的事儿做不毫无疑问、概率不大的推断，或实际上压根没产生，译为“或许……”。如：

At FloridaPower’s Crystal River plant， apotentially serious leakage of radioactive water may have been unknowinglycaused by an electrician.

2.表明虚拟语气。

1） needn’t have 过去分词，表明干了无须做的事，等同于“didn’t need to do”，译为“实际上没必要……”。如：

You needn’thave come over yourself.

As it turnedout to be a small house party， we__________ so formally.

[A] needn’tdress up [B]did not need have dressed up

[C] did notneed dress up [D] needn’t have dressed up

（沒有需要穿的那麼宣布，反映是讲话者的提议，具体結果是不是确实穿的很宣布沒有明确，回答为D）

2）should have 过去分词，表明应当做某件事但其实未做，译为“本应当……”should not have过去分词表明本不应该做某件事但事实上干了，译为“本不应该……”。如：

I regrethaving left the work unfinished； Ishould have planned everything ahead carefully.

我原本应当事前认真地把一件事儿整体规划的非常好，但其实创作者或是沒有规划好，以致工作中都没有进行。

3） ought to have 过去分词，表明姿势按道理该发生了，但其实未产生，译为“该……”，与should 的进行式含意相近。如：

Ｔheporter ought to have called the fire-brigade as soon as he saw the fire in thestock，which went up in smoke .

4） could have 过去分词，表明以往原本能够 做但却未做，译为“彻底能够 ……”。这一点与ought/should/ have 过去分词使用方法类似。如：

What you saidis right，but you could have phrased it more tactfully.

5） may/ might have 过去分词，表明以往能够 做但实际上未做，译为“（那般）或许会……”。如：

It might havebeen better to include more punchy statistics and photos of equipment in theintroduction to further assist first-time office automation managers.