考研的英語語法速成：情態動詞現在完成式用法
情態動詞現在完成式主要有兩個功能：表示已經發生的情況和表示虛擬語氣。在這兩個方面must/mustncan/cannneed/neednmay/maynmight/mightnshould/shouldnought等情態動詞+完成式表示的意思是有一定區別的
1.表示已經發生的情況。
1)must have+過去分詞，表示對已發生情況的肯定推測，譯為(昨天)一定。如：
My pain apparent the moment I walked into the room, for the first man I met asked sympathetically: Are you feeling all right?
[A] must be [B] had been [C] must have been [D] had to be
(答案為C)
2)cant / couldnt have+過去分詞，表示對已發生情況的否定推測，譯為(昨天)一定沒。如：
Mary my letter; otherwise she would have replied before now.
[A] couldnt have received [B] ought to have received
[C] has received [D] shouldnt have received
(答案為A)
3)may / might have +過去分詞，表示對已發生的事情做不肯定、可能性很小的推測，或事實上根本沒發生，譯為也許。如：
At Florida Powers Crystal River plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.
2.表示虛擬語氣。
1) neednt have + 過去分詞，表示做了不必做的事，相當于didnt need to do,譯為其實沒必要。如：
You neednt have come over yourself.
As it turned out to be a small house party, we so formally.
[A] neednt dress up [B]did not need have dressed up
[C] did not need dress up [D] neednt have dressed up
2)should have +過去分詞，表示應該做某事但實際上未做，譯為本應該should not + have過去分詞表示本不應該做某事但實際上做了，譯為本不應該。如：
I regret having left the work unfinished; I should have planned everything ahead carefully.
我本來應該事先認真地把每件事情規劃的很好，但實際上作者還是沒有規劃好，以至工作沒有完成。
3) ought to have +過去分詞，表示動作按理該發生了，但實際上未發生，譯為該，與should 的完成式含義類似。如：
The porter ought to have called the fire-brigade as soon as he saw the fire in the stock, which went up in smoke .
4) could have +過去分詞，表示過去本來可以做但卻未做，譯為完全可以。這點與ought/should/ have +過去分詞用法相似。如：
What you said is right, but you could have phrased it more tactfully.
5) may/ might have +過去分詞，表示過去可以做但實際未做，譯為(那樣)也許會。如：
It might have been better to include more punchy statistics and photos of equipment in the introduction to further assist first-time office automation managers.
情態動詞現在完成式主要有兩個功能：表示已經發生的情況和表示虛擬語氣。在這兩個方面must/mustncan/cannneed/neednmay/maynmight/mightnshould/shouldnought等情態動詞+完成式表示的意思是有一定區別的
1.表示已經發生的情況。
1)must have+過去分詞，表示對已發生情況的肯定推測，譯為(昨天)一定。如：
My pain apparent the moment I walked into the room, for the first man I met asked sympathetically: Are you feeling all right?
[A] must be [B] had been [C] must have been [D] had to be
(答案為C)
2)cant / couldnt have+過去分詞，表示對已發生情況的否定推測，譯為(昨天)一定沒。如：
Mary my letter; otherwise she would have replied before now.
[A] couldnt have received [B] ought to have received
[C] has received [D] shouldnt have received
(答案為A)
3)may / might have +過去分詞，表示對已發生的事情做不肯定、可能性很小的推測，或事實上根本沒發生，譯為也許。如：
At Florida Powers Crystal River plant, a potentially serious leakage of radioactive water may have been unknowingly caused by an electrician.
2.表示虛擬語氣。
1) neednt have + 過去分詞，表示做了不必做的事，相當于didnt need to do,譯為其實沒必要。如：
You neednt have come over yourself.
As it turned out to be a small house party, we so formally.
[A] neednt dress up [B]did not need have dressed up
[C] did not need dress up [D] neednt have dressed up
2)should have +過去分詞，表示應該做某事但實際上未做，譯為本應該should not + have過去分詞表示本不應該做某事但實際上做了，譯為本不應該。如：
I regret having left the work unfinished; I should have planned everything ahead carefully.
我本來應該事先認真地把每件事情規劃的很好，但實際上作者還是沒有規劃好，以至工作沒有完成。
3) ought to have +過去分詞，表示動作按理該發生了，但實際上未發生，譯為該，與should 的完成式含義類似。如：
The porter ought to have called the fire-brigade as soon as he saw the fire in the stock, which went up in smoke .
4) could have +過去分詞，表示過去本來可以做但卻未做，譯為完全可以。這點與ought/should/ have +過去分詞用法相似。如：
What you said is right, but you could have phrased it more tactfully.
5) may/ might have +過去分詞，表示過去可以做但實際未做，譯為(那樣)也許會。如：
It might have been better to include more punchy statistics and photos of equipment in the introduction to further assist first-time office automation managers.
