2023年職稱英語考試常用語法詳解之情態動詞的完成式
2023年職稱英語考試常用語法詳解:情態動詞的完成式
情態動詞的完成式：
can / may / should / ought to / must / need等動詞稱為情態動詞。情態動詞有三大特征：一是無人稱和數的變化，二是后面跟的動詞不帶to，三是后面 + not構成否定式，比較：
He neednt go there so early.
You do not need to be an expert to make this simple design.
在講解情態動詞完成式前，先將一般式中應注意的幾個問題提一下，以引起必要的重視。
1.情態動詞一般式中應注意的幾個問題：
注意以下用法的習慣與區別：
He must be a doctor.
否定：He cant be a doctor.
又如：They cant be working now.
May I go now?
回答：Yes, please. / Please dont.
have to 與 must
1) 當強調外界原因時，2)當與將來時結合時，用have to，
例如醫學全在.線.提供, www.med126.com：
Since it is raining, we have to sty indoors.
You will have to hurry if you want to catch the 9:30 train.
3) 表示自然規律或必然結果，用must，
例如：
All men must die.
can 與be able to
can表示能力，但不一定做了或做成了;be able to 表示有能力并且做成了，相當于succeed in doing, 例如：
The patient is able to walk now.
The patient can walk now.
Shall I / we? 表示征求對方意見; + shall表示允諾或警告，例如：
Shall I fetch a doctor for you?
You shall be sorry for what you have done.
Will you.? 表示請求， 例如：
Don be late for the meeting next time, will you?
比較：I would remind you that smoking is forbidden here.
neednt 的肯定式為must，例如：
You neednt see him, but I must.
cannot but + 原形動詞， 例如：
I cannot but tell you the truth.
2.情態動詞的完成式：
情態動詞的一般式用于表達現在或將來的情況，而情態動詞的完成式則用來表達已經發生的事情，例如：你不應該來得那么晚。這是對已經發生的事情表示自己的看法：You shouldnt have come so late.
將常用、常考的幾個情態動詞完成式列表說明如下：
It must have rained last night; the ground is wet.(昨晚準是下雨了，地上濕漉漉的。)
The baby was cut badly; she shouldnt (oughtnt to) have let him play with the scissors. (孩子傷得很厲害;她不該讓他玩剪刀。)
She may have known the news; she is crying. (她可能已經知道那個消息了;她在哭。)
You neednt have bought that dictionary; I have got a spare one. (你實際上沒有必要買那本字典;我有一本多余的。)
由于在沒有情景的情況下很難區分情態動詞一般式和完成式，例如你不該去，究竟是You shouldnt go there. 還是 You shouldnt have gone there, 因此考試的時候往往會給出情景，這對判題非常重要，如上面表格例子中的the ground is wet，the baby was cut badly，she is crying, 都是題目所給的情景。
2023年職稱英語考試常用語法詳解:情態動詞的完成式
情態動詞的完成式：
can / may / should / ought to / must / need等動詞稱為情態動詞。情態動詞有三大特征：一是無人稱和數的變化，二是后面跟的動詞不帶to，三是后面 + not構成否定式，比較：
He neednt go there so early.
You do not need to be an expert to make this simple design.
在講解情態動詞完成式前，先將一般式中應注意的幾個問題提一下，以引起必要的重視。
1.情態動詞一般式中應注意的幾個問題：
注意以下用法的習慣與區別：
He must be a doctor.
否定：He cant be a doctor.
又如：They cant be working now.
May I go now?
回答：Yes, please. / Please dont.
have to 與 must
1) 當強調外界原因時，2)當與將來時結合時，用have to，
例如醫學全在.線.提供, www.med126.com：
Since it is raining, we have to sty indoors.
You will have to hurry if you want to catch the 9:30 train.
3) 表示自然規律或必然結果，用must，
例如：
All men must die.
can 與be able to
can表示能力，但不一定做了或做成了;be able to 表示有能力并且做成了，相當于succeed in doing, 例如：
The patient is able to walk now.
The patient can walk now.
Shall I / we? 表示征求對方意見; + shall表示允諾或警告，例如：
Shall I fetch a doctor for you?
You shall be sorry for what you have done.
Will you.? 表示請求， 例如：
Don be late for the meeting next time, will you?
比較：I would remind you that smoking is forbidden here.
neednt 的肯定式為must，例如：
You neednt see him, but I must.
cannot but + 原形動詞， 例如：
I cannot but tell you the truth.
2.情態動詞的完成式：
情態動詞的一般式用于表達現在或將來的情況，而情態動詞的完成式則用來表達已經發生的事情，例如：你不應該來得那么晚。這是對已經發生的事情表示自己的看法：You shouldnt have come so late.
將常用、常考的幾個情態動詞完成式列表說明如下：
It must have rained last night; the ground is wet.(昨晚準是下雨了，地上濕漉漉的。)
The baby was cut badly; she shouldnt (oughtnt to) have let him play with the scissors. (孩子傷得很厲害;她不該讓他玩剪刀。)
She may have known the news; she is crying. (她可能已經知道那個消息了;她在哭。)
You neednt have bought that dictionary; I have got a spare one. (你實際上沒有必要買那本字典;我有一本多余的。)
由于在沒有情景的情況下很難區分情態動詞一般式和完成式，例如你不該去，究竟是You shouldnt go there. 還是 You shouldnt have gone there, 因此考試的時候往往會給出情景，這對判題非常重要，如上面表格例子中的the ground is wet，the baby was cut badly，she is crying, 都是題目所給的情景。
