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Bài 2 : CÂU ĐIỀU KIỆN
(Conditional Sentence)
Một câu điều kiện có hai mệnh đề : mệnh đề chỉ điều kiện (tức mệnh đề phụ) còn được
gọi là mệnh đề có if (If-clause) và mệnh đề chỉ kết quả còn được gọi là mệnh đề chính
(main clause).
- If he works harder, he will succeed in his examination.
(if-clause) (main clause)
Chúng ta cũng có thể đặt mệnh đề chính ở đầu câu :
- He will succeed in his examination if he works harder.
Trong tiếng Anh có 3 loại câu điều kiện chính :
* Type I : ĐIỀU KIỆN CÓ THỂ XẢY RA ĐƯỢC (probable condition)
1/ Ý nghĩa : Loại điều kiện này dùng để diễn tả một sự việc có thể xảy ra hoặc không
thể xảy ra ở hiện tại hoặc tương lai; nhưng chúng ta có nhiều hy vọng nó xảy ra.
2/ Thì của động từ :
If- clause Main clause
Simple present Simple future
(shall / will + verb)
- If the rain stops, we shall go for a walk.
- He will come if you call him.
* Ngoài ra chúng ta còn có thể dùng các khiếm khuyết động từ như : CAN, MUST,
MAY … để thay cho shall hoặc will ở mệnh đề chính.
- If you ask me, I can help you.
- You must study harder if you want to pass the coming exam.
* Mệnh đề chính có thể là một mệnh lệnh hoặc thỉnh cầu :
- Come to me if you need help.
- If you have time, perfect your English.
* Type II : ĐIỀU KIỆN KHÔNG CÓ THẬT Ở HIỆN TẠI. (Present- unreal Con)
1/ Ý nghĩa : Loại điều kiện này diễn tả một điều kiện khó có thể xảy ra hay một
sự việc không thực hiện được ở hiện tại hoặc tương lai.
2/ Thì của động từ :
If-clause Main clause
Past Subjunctive
(Quá khứ giả định) Present Conditional
( Should / would + verb)
- If I had a lot of free time, I would go swimming.
(= I haven’t got free time, so I won’t go swimming)
- If Tom were here, he would know the answer.
(= Tom isn’t here, so he doesn’t know the answer.)
- I would call him if I knew his number.
(= I don’t know his number, so I won’t call him)
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* Quá khứ giả định là hình thức quá khứ đơn của các động từ ngoại trừ động từ “to
be” chỉ có một hình thức WERE cho tất cả các ngôi.
* COULD, MIGHT… có thể được dùng để thay thế cho should hay would.
- If John worked hard, he could pass his exam.
* Type III : ĐIỀU KIỆN KHÔNG CÓ THẬT Ở QUÁ KHỨ. (Past-unreal
Condition)
1/ Ý nghĩa : Loại điều kiện này dùng để diễn tả một điều kiện hoàn toàn không thực
hiện được hoặc không xảy ra trong quá khứ.
2/ Thì của động từ :
If-clause Main clause
Past perfect Perfect Conditional
(Should/ would have + past participle)
- If he had had a lot of money, he would have bought a bigger house.
- I would have taken you to the movie if you had come to see me yesterday.
* “If” có thể được lược bỏ đi nếu có sự đảo ngữ (thường được dùng trong hình thức
nhấn mạnh).
- Were I rich, I would help you.
(= If I were rich, I would help you.)
- Had he known the truth, he would have been very angry.
(= If he had known the truth, he would have been very angry)
* Ngoài liên từ “if” ra, câu điều kiện còn được bắt đầu bằng các liên từ khác như :
suppose, supposing that (giả sử như), on the condition that (với điều kiện là), as long
as, so long as, provided that (miễn là), in case (trong trường hợp) , even if ( ngay cho
là)... - As long as you return the book by Saturday, I will lend it to you with
pleasure.
* Hai tiếng có nghĩa phủ định : unless (trừ phi), but for (nếu không)
- He won’t come unless you call him.
(= He won’t come if you don’t call him.)
- But for the storm, he would have arrived much earlier.
EXERCISE I : Rewrite the sentences , using conditional clauses.
1/ I (do) if I (have) time.
- I will do it if I have time. (type 1)
- I would do it if I had time. (type 2)
- I would have done it if I had had time. (type 3)
2/ If she (not try), she (not succeed).
- ____________________________________________________
- ____________________________________________________
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- ____________________________________________________
3/ If I (see) her, I (tell) her.
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
4/ (You do) it if I (ask) you ?
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
5/ If I (be) ill, I (stay) at home.
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
6/ What (you do) if the bus (not come).
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
7/ I (be) sorry if she (leave).
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
8/ I (not stay) in this job if I (can find) another one.
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
9/ They (get) wet if it (rain).
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
10/ It (not bite) you unless you (move)
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
11/ We (go) out unless it (stop) snowing.
- ____________________________________________________
- ____________________________________________________
- ____________________________________________________
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EXERCISE II: Put the verbs in brackets in correct tenses.
1/ If I (have) ________ a typewriter, I could type it myself.
2/ If I had known that you were in hospital , I (visit) ________ you.
3/ You could make much progress if you (attend) ________ class regularly.
4/ If I (know) ________ his telephone number, I would give it to you.
5/ If you (arrive) ________ ten minutes earlier, you would have got a seat.
6/ If he (study) ________ harder, he can pass an exam.
7/ She may be late if she (not hurry) ________.
8/ Tell him to ring me if you (see) ________ him.
9/ If you (speak) ________ more slowly,he might have understood you.
10/ What (you do) ________ if you got fat ?
Exercise III : Supply the correct verb tense.
1/ If you are kind to me, I (be) _______ good to you.
2/ He (come) _______ if you waited.
3/ If you (ring) _______ the bell, the servant would come.
4/ If I had known that the baby was hungry, I (feed) _______ him.
5/ If it (not, rain) _______ a lot, the rice crop wouln’t grow.
6/ If today (be) _______ Sunday, we wouldn’t have to work.
7/ If she had had your address, she (write) _______ to you.
8/ We lost the match. If you (play) _______ for us, we (win) _______.
9/ So long as you return the book by Saturday, I (lend) _______ it to you with
pleasure.
10/ They would not be paid unless they (do) _______ their work well.
11/ Provided he (not, be) _______ interrupted, he can finish the work on time.
12/ If it (be) _______ convenient, let’s meet at three o’clock.
13/ If I became very rich, I (build ) _______ a hospital for the poor.
14/ If he (give) _______ up smoking, as his doctor orders, he will be soon well
again.
15/ He (not, have) _______ an accident if he had not been driving so fast.
16/ If she (write) _______ more carefully, she might not have made too many
mistakes.
17/ You would have to stay in bed unless your health (improve) _______.
18/ Did she have more practice, she (speak) _______ English better.
19/ Had I known that she was sick, I (visit) _______ her.
20/ Supposing World War III (happen) ________, human civilization (be)
_______ destroyed.
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EXERCISE IV : Put “if” or “unless” into these spaces.
1/ ________ we hurry, we’ll miss the bus.
2/ Will you phone me ________ you come to England ?
3/ ________ you see Jane, ask her to contact me.
4/ You’ll never pass your exam ________ you don’t work harder.
5/ Liverpool won’t win ________ they begin playing better.
6/ ________ you forget our address, you can find it in the phone book.
7/ You won’t pass your driving test ________ you drive more carefully.
8/ He’ll be ill ________ he doesn’t stop worrying so much.
9/ We’ll go to the beach tomorrow ________ it’s raining.
10/ We’ll never get there on time ________ the train leaves soon.
EXERCISE V : Use “if” in place of “unless”
1/ We won’t go out unless it stops raining.
-____________________________________________________________
2/ I will call the police unless you give back my bicycle.
-____________________________________________________________
3/ You wouldn’t be able to do this exercise unless your English were good.
-____________________________________________________________
4/ Unless we had enough rain, we couldn’t grow rice.
-____________________________________________________________
5/ The fishermen couldn’t have caught a lot of fish unless they had had good nets.
-____________________________________________________________
6/ I wouldn’t buy it unless I could afford it.
-____________________________________________________________
7/ I would refuse to go unless they paid my expenses.
-____________________________________________________________
8/ I don’t agree with his economic policy. I wouldn’t vote for him unless he
changed it.
-____________________________________________________________
9/ He wouldn’t have written unless he had heard news.
-____________________________________________________________
10/ You might not have a terrible toothache unless you went to the dentist
regularly.
-____________________________________________________________
EXERCISE VI : The following sentences are first, second or third conditional. Put the
verbs in brackets into the appropriate form.
1/ We wanted to go out yesterday but the weather was terrible. If it (be) … had
been … a nice day, we (go) … would have gone … for a picnic.