1.    You       better after you have something to eat.

A.  feel                    B. will feel

C. have felt            D. would feel

2.    Susan              chess when she was a child.

A.  played               B. was playing

C. have played      D. had played

3.    Our teacher .........  us yesterday that he................England several times.

A.  told / visited        B. told / would visit

C. told / has visited D. told / had visited

4.    He ........asleep while he ..............his homework.

A.  fell / did             B. fell / had done

C. fall/ is doing      D. fell / was doing

5.    You.........the value of health until you..............it.

A.  won’t know / lose

B.  haven’t known / lose

C.  haven’t known  / lost

D.  wouldn’t know / had lost

6.    He asked me why I .............there so early.

A.  had come         B. came

C. have come       D. was coming

7.While I was writing a letter, the children.......outside.

A.  was playing       B. were playing

C. are playing        D. have played

8.    After my sister .........     her clothes, she began to study.

A.  washes             B. has washed

C. had washed      D. would wash

9.    We had already begun to our walk when it  ........    to rain.

A.  begins               B. began

C. has begun                     D. had begun

10.  They (come).....          with us as soon as they finish work.

11.  A: How long   ..........               you    ...........  in this school?

A.  did / study         B. do / study

C. have / studied D. were / studying

B: I (24)   .......         here for two years. When I (25)   .........    the 5^th year, I (25)  ..........      able to get a diploma.

24.  A. studied     B. study

C. have studied    D. were studying

25.  A. had finished / would be

B.  finished / had been

C.  have finished / will be

D. finished / was

26.  Do not make a noise: the children    .........            to sleep.

A.  try                     B. have tried

C. were trying        D. are trying

27.  I...........      with you on that subject.

A.  am agree          B. am agreed

C. agreeing           D. agree

28.  I...........          about this for some time now.

A.  know                 B. am knowing

C. knew                 D. have known

Complete the following sentences.

1.    We have not seen Mr and Mrs Baker........a long time.

A.  after                  B. for

C. before               D. since

2.  Don’t leave..........    I arrive.

A.  after                  B. when

C. till                      D. since

3.    We have not received any letter from him  ...........  he left 4 months ago.

A.  after                  B. when

C. before               D. since

4.    My grandmother died        ...........          she had been ill for a long time.

A.  after                  B. when

C. before               D. since

5.    Last night I went to bed  ...............                        .

A.  after I have finished my homework

B.  before I had dinner

C. when she came to see me

D. as soon as I turned off the light

6.    We will have a big party  ................                        .

A.  when you go to bed

B.  as soon as went back to Vietnam.

C. after we have dinner

D. before we leave for the USA

7.    They will leave           ....................                         .

A.  as soon as they will finish work

B.  as soon as they had finished work

C. as soon as they finish work

D. as soon as they finished work

8.    He has been working for this company ..............

A.  since he had left school

B.  when he left school

C. since he leaves school

D. since he left school

9.    I slipped on the ice while..................

A.  I am skiing             B. I was skiing

C. I have been skiing D. I went skiing

10.  He had finished all his work

A.  as soon as he went to work.

B.  after he went to work.

C. while he was going to school

D. before he left his office

11.  By the time I left school this morning, .

A.  I had studied five lessons.

B.  I have studied five lessons.

C. I will study five lessons.

D. I studied five lessons.

12.  I have known my neighbours...............                     

A.  since a long time ago

B.  when moved here in 1990

C. since we went to the same school

D. for 2 months ago

13.  We last wrote to each other five years ago

A. We haven’t written to each other for five years.

B. We haven’t written to each other since five years

C. We haven’t written to each other five years ago.

D.  It was five years since we wrote to each other.

14.  They last saw each other thirteen years ago.

A.  It was thirteen years since they had seen each other.

B.  They haven’t seen each other for thirteen years ago.

C. They haven’t seen each other since thirteen years.

D.  It is thirteen years since they last saw each other.

15.  The phone rang immediately after I sat down at the table.

A. We had hardly sat down at the table, when the phone rang

B. We had no sooner sat down at the table, when the phone rang

C.  Before we sat down at the table, the phone had rang

D. We sat down at the table, when the phone rang

Exercise 2

1.  They have worked in that company since 1999.

They began ........................................................

2.  He started studying English ten years ago.

He has................................................................

3.  My father began smoking when he was 18 My father has .....................................................

4.  He fell ill on Friday.

He has................................................................

5.  During our lunch someone rang the bell. While we.............................................................

6.  I haven’t been to the dentist for 6 months. The last time ......................................................

7.  He did his work and then he went home.  After he ..............................................................

8.  I haven’t heard from him for a long time.

It’s a long time ....................................................

9.  He came home and found his son watching TV.

When he.............................................................

10.  She has never eaten such good eel soup before.

It is the best........................................................

1)  Marc has his own company. He started it in 1999.

 ..........................................................................................................................

2)  Franca works as an accountant. She qualified in 2001.

 ...........................................................................................................................

3)  Claude and Anna are married. They got married six months ago.

 ...........................................................................................................................

4)  Leon is learning Japanese. He began last year.

............................................................................................................

5)  Mike lives in Dublin. He moved there three years ago.

.....................................................................................................................

6)  The company is manufacturing electrical goods. It started five years ago.

....................................................................................................................

7)  I last saw her two weeks ago

I haven’t........................................................................................................

8)  The last time she phoned me was two days ago

She hasn’t .....................................................................................................

9)  We started / began learning English when we were in grade 6.

We have .........................................................................................................

10)  It is three months since they last went to the cinema.

They haven’t.........................................................................................

11)  He last wrote to her in 2003.

He hasn’t ........................................................................................

12)  When did you start working for this company?

How long ....................................................................................................

Một phân tử mARN có 250 uraxin, chiếm 25% tổng số ribônuclêôtit. Gen tổng hợp ra phân tử mARN đó có tổng số nuclêôtit là bao nhiêu?

Một phân tử mARN có 250 uraxin, chiếm 25% tổng số ribônuclêôtit. Gen tổng hợp ra phân tử mARN đó có tổng số nuclêôtit là bao nhiêu?

. Một gen có chiều dài 5100A⁰ và có 3900 liên kết H, mạch 1 có A= 255, G = 360. Số lượng A và G lần lượt trên mạch thứ 2 là:

A. A= 255, G= 360         B. A= 345, G= 540        C. A= 540, G= 345         D. A= 630, G= 255

1.    This is the first time I have eaten such good soup.

→This  is  the  best .............................................................................

→I have ................................................................................................

→Never before....................................................................................................

2.    My parents are busy. They try to spend as much time with us as possible.

→Although .................................................................................................

→Busy  as  .........................................................................................................

→However  ...................................................................................................

→In  spite of....................................................................................................

3.    The last time I met you was four years ago

→I haven’t...........................................................................................................

→I last.................................................................................................................It’s  been /  It is ...........................................................................................

4.    She got up early. She wanted to prepare the breakfast for her children.

→In   order..........................................................................................................

→She got up early so that ................................................................................

Chứng minh \(\dfrac{f\left(x\right)}{g\left(x\right)}=\dfrac{f'\left(x\right)}{g'\left(x\right)}\)

1.    It started to rain right after they went out.

→  No sooner......................................................................................................

→Hardly/  Scarcely/  Barely ..............................................................................