VI. Choose the best answer:

1. They ................... students yesterday.   a. am                    b. is             c. was         d. were
2.They .............  doctors two years ago.    a. am                    b. is             c. was         d. were
3. They ............... farmers last month.       a. are                    b. is             c. was         d. were
4. We ....... nurses yesterday.           a.are            b. is             c. was         d. were
5.  The weather  ........ cold yesterday.       a.aren’t       b. isn’t        c. wasn’t     d. weren’t
6.  I .........a pupipl last week.                    a.aren’t       b. isn’t        c. wasn’t     d. weren’t
7. These hats .......new yesterday.    a.aren’t       b. isn’t        c. wasn’t     d. weren’t
8.  My parents........teacchers two years ago. a.are       b. is                     c. was         d. were
9. He .............a mechanic last Monday. a.aren’t           b. is             c. wasn’t     d. weren’t

10. ... he an engineer yesterday. No, he ......

a.is/ is n’t            b.are/aren’t                    c.was/wasn’t                  d.were/weren’t

11. .......It hot last week?                           a. am                    b. is             c. was         d. were
12. The shops ...open last Monday.                    a. am                    b. is             c. was         d. were
13.  .... you a teacher two years ago? Yes ,I.......

a.is/ is n’t   b.are/aren’t                    c.were/wasn’t                 d.was/weren’t
14.  Where ......Nam from yesterday?                  a. am                    b. is             c. was         d. were
15.  Why .........they unhappy last Tuesday?       a. am                    b. is             c. was         d. were
16. I ... your trip to Nha Trang two years ago.
a.remember          b.remembers        c.remembered       d.rememberred
17. Ba ........ the cap all day yesterday.      a. wear        b. wears      c. weared    d. wore
18. We ..........a lot of fish yesterday.                   a. eated      b. ate                    c. eats         d. eat
19. Her aunt ......... her to see Cham Temple last year.

a .taked                         b. took                  c. take                   d. takes
20. Tuan ......... a new bike yesterday.                 a. haved      b. has                   c. had           d. have
21. She............... a new ruler yesterday.

a.didn’t buy                  b.doesn’t bought c.did buy                        d.didn’t bought
22. He ........................ with his parents about his vacation in Da Lat last year.
a. don’t talk                  b. doesn’t talked c. didn’t talked               d. talked
23. They........... school yesterday
a. didn’t comed             b. didn’t come      c. doesn’t comed            d. doesn’t come
24. The windows ........... yesterday
a. didn’t close               b. didn’t closed    c. doesn’t closed            d. doesn’t close
25. We ………..at home at 7 p.m last Monday.
a. didn’t return              b. didn’t returned           c.doesn’t return             d. doesn’t returned
26. She ...............fish and crab yesterday.
a. doesn’t eat                b. doesn’t eated    c. didn’t eat                             d. didn’t ate
27. Lan ......... Ho Chi Minh city two years ago.
a. didn’t go                   b. doesn’t went    c. didn’t went                 d. doesn’t go
28. My parents ........to Vung Tau last week.
a.don’t taked                 b. don’t took        c.didn’t take                   d.didn’t takes
29. We ...............a lot of friends in Ha Noi two years ago.
a. don’t have                 b. don’t has                   c.didn’t had                             d. didn’t have
30. …………….. Lan and Hoa your school two years ago? 

a. Are                           b. Is                      c. Was                            d. Were
31. What.... they ...........last week?
a. do .. play                   b. did ... play        c. do .... played              d. did ..... played
32. What .............. Hoa .............. on yesterday?

a. did... try                    b. do... try            c. did..... tryed                d. do..... tryed
33. Who ........to about the film on TV last Monday?
a. talk                            b. talks                 c. talked                         d. talking
34.Where.................. they ............... on their way back last Sunday?
a. did.. stop                   b. do... stop                   c. did... stopped             d. do .. stopped
35. What ……….. the student .......... at school two years ago?
a.did ... wears                b.did ... wear        c.do... wears                            d. does .. wear
36. Where you .................... the cake yesterday?

a. was... put                  b.were.. put                    c. did ... put                             d. do... put
37. What time ………………. you ...................... home for school yesterday?
a. was... leave                b.were.. leave       c. did ... leave                 d. do... leave
38. What …………….  Ba........... from Liz last week?
a. was... receive             b.were… receive   c. did ... receive              d. do... receive
39. How long ……………. he..........his test yesterday?

a. was... do                    b.were.. do           c. did ... do                     d. does... do
40. What time …………….. you ............to bed last night?

a. was... go                    b.were.. go            c. did ... go                     d. does... go
41. We .........to Dalat for last Tet holiday.          a. go            b. goes        c. going       d. went
42. He ............. a lot of friends in Ho Chi Minh city 3 years ago?
a Do.... have                  b.Did... has                    c.Did...had                     d. Did… have

43. His uncle ........ him to see Tri Nguyen aquarium last week.

a .taked                b. took                  c. take                   d. takes
44. ………….. Liz ......... a lot of souvenirs yesterday?

a.Did… buy                  b. Does… bought           c. Did… bought             d. Do … bought
45. ………… they .........the fish in the big bag last Sunday?

a. Was... put                 b.Were… put       c. Did ... put                            d. Do... put
46. …………. they............. meat in her meals in Vung Tau yesterday?
a. Was... eat                  b.Were.. eat                    c. Did ... eat                             d. Do... eat
47. We ............ the cap with a dolphin om it yesterday.

a. wear                          b. wears                c. weared                        d. wore
48. Liz............... Ba some English last week.

a. teach                          b. teached             c.thaught                        d. taught
49. Ba and Tan ........... their trip to Nha Trang last month.
a.remember                   b.remembers         c.remembered                 d. rememberred
50. ………….. Nam............to Ha Noi last week?

a.Was... return              b.Were.. return     c. Did ... return              d. Does... return
51. I ............to Ben Thanh market last Monday. a. go b. goes        c. goed        d. went
52. He..............up at 7 o’clock yesterday.           a. get                    b. getted      c. got                    d. to get
53. What time …….. you .......to bed last night?

a. Was... go                   b.Were… go         c. Did ... go                              d. Does... went

54. She .............to work last weekend.

a. didn’t go                   b. doesn’t went    c. didn’t went                 d. doesn’t go
55.  Lan..............her at the party 3 years ago. a. meet b. meted      c. met          d. meeted
56. Last summer vacation,………… her Mom........her a new bike?
a.Did.. buy          b. Does… buy      c. Did… bought             d. Do .. bought
57. When …………. he.......... for work last week?

a.was...leave                  b.were…leave       c. did ... leave                 d. does... leave
58. What ………….you............ yesterday?

a. was... do                    b.were… do                   c. did ... do                     d. do... do
59. We...........to learn English 3 years ago. a. begin     b.began       c. begun      d. begined
60. I ............an engineer last week.             a. am                   b. is             c. was         d. were
61. They ..........at home yesterday.         a.aren’t         b. is n’t       c. wasn’t     d. weren’t
62- He ......the shirt last week.                           a. wear                   b. wears      c. weared    d. wore
63. We ...........here yesterday.                           a. am            b. is             c. was         d. were
64.  ………….you ..........to school yesterday?

a. Was... go                   b.Were.. go                   c. Did ... go                    d. Do... went
65. Where ………………. he................... yesterday?

a. was... go                    b.were… go                   c. did ... go           d.does…went
66. I ................ sick last night.                  a. am                    b. is             c. was                   d. were
67. Why ……….. you ............... to class yesterday?
a. didn’t… comed         b. didn’t... come   c. doesn’t… comed        d. doesn’t… come
68. We ............in the library yesterday.     a. am                    b. is             c. was         d. were
69. Hoa ...........a lot of things for her birthday party yesterday.

a. buy                  b. buyed               c. bought              d. buys
70. How …………… you ........... to school yesterday?
a.was...go            b.were… go                   c. did ... go           d. does... go

V. Use the Past form of the verbs:

1. Yesterday, I (go)______ to the restaurant with a client.
2. We (drive) ______ around the parking lot for 20 mins to find a parking space.
3. When we (arrive) ______ at the restaurant, the place (be) ______ full.
4. The waitress (ask) ______ us if we (have) reservations.
5. I (say), "No, my secretary forgets to make them."
6. The waitress (tell)______ us to come back in two hours.
7. My client and I slowly (walk) ______ back to the car.
8. Then we (see) ______ a small grocery store.
9. We (stop) in the grocery store and (buy) ______ some sandwiches.
10. That (be) ______ better than waiting for two hours.
11. I (not go) ______ to school last Sunday.
12. She (get) ______ married last year?
13. What you (do) ______ last night? - I (do) ______ my homework.
14. I (love) ______ him but no more.
15. Yesterday, I (get) ______ up at 6 and (have) ______ breakfast at 6.30.

1. She (spend) ____ all her money last week.
2. Mum (not spend) ___________ any money on herself.
3. I (lend) __________ my penknife to someone, but I can't remember who it was now.
4. John and his father (build) ___________ the cabin themselves last year.
5. My parents (sell) ____________ the stereo at a garage sale.
6. ___________You (tell) ___________ anyone about this yesterday?
7. The unidentified plant (bear) ___________ gorgeous flowers.
8. She (tear) ___________ the letter to pieces and threw it in the bin.
9. He often (wear) ___________ glasses for reading.
10. Before God He (swear) ___________ he was innocent
11. Yesterday Clouds (creep) ___________ across the horizon, just above the line of trees.
12. We both (sleep) ___________ badly that night.
13. She (weep) ___________ for the loss of her mother.
14. Jane (keep) ___________ the engine running.
15. A huge wave (sweep) ___________ over the deck
16. Mum (pay) ___________ for my driving lessons.
17. He (lay) ___________ his hand on my shoulder.
18. He (break) ___________ the biscuit in half and handed one piece to me.
19. He (choose) ___________ his words carefully as he (speak) ¬___________.
20. He …………………to the zoo last Sunday (go)
21. She (not /watch)………………………………TV last night
22. They (meet)…………………………their friends at the movie theater last week
23. What……………you (do)…………………last night
24. ……………………… they (buy)…………………a new car two days ago?

25. We ………….. (have) a lot of homework yesterday.

1) I (go)............................to Ben Thanh market last Monday
2) He (get)..............................up at 7 o’clock yesterday.
3) What time you (go) .....................to bed last night?
4) She ( not go)..................................to work last weekend.
5) Lan (meet).................................her at the party 3 years ago.
6) Last summer vacation,Mom (not buy).............................me a new buy?
7) When he (leave)............................... for work last week.
8) What you (do)................................. yesterday?
9) We (begin)....................................to learn English 3 years ago.
10) She (be).........................................an engineer last week.
11) Lan (be not)...................................at home yesterday.
12) He (wear) .....................................the shirt last week.
13) They (be ) ................................here yesterday.
14) You (go) ...............................to school yesterday?
15) Tam (be)...................................... at home last night? – Yes, he (be).
16) Where he (go)........................................ yesterday?
17) I (be)......................................... sick last night.
18) Why you (not come ).............................. to class yesterday?
19) We (be) ................................in the library yesterday.
20) Hoa (buy) ...................................a lot of things for her birthday party.
21) What time you (leave) ........................................home for school yesterday?

IV. CHOOSE THE BEST ANSWER

1. He _______ at school two days ago.

A. isn’t                          B. won’t be                    C. wasn’t

2. What time _______ go to bed last night?

A. did you go                          B. do you go                            C. did you went

3. How ______ your vacation in Hoi An last week?

A. is                               B. was                                     C. did

4. He ______ here yesterday.

A. doesn’t come             B. didn’t came               C. didn’t come    

5. What ___ you ____ last Saturday?

A. do – do                      B. did – did                    C. did – do

6. We didn’t _______ each other 10 years ago.

A. see                                      B. saw                                     C. seeing

7. ______ did you meet him? – Yesterday evening.

A. When                        B. Where                        C. What time

8. I had a good time ______ my parents in Hue.

A. for                                       B. with                           C. at

9. I ________ seafood when I was in Nha Trang.

A. didn’t ate                            B. did ate                       C. didn’t eat

10. _______ you see that movie last night?

A. Were                         B. Was                           C. Did                                        

Gọi k là số lần nhân đôi của gen.

x là số Nu của gen

Theo bài ra ta có :

27000=x(2^k-1) mà theo vào 1500<x<2000

nên x = 1500 hoặc x=1800

Nếu x=1500 thì k không nguyên dương

Nếu x=1800 thì k=4(thỏa mãn)

Nên số Nu của gen là 1800Nu.

b) Có số Nu môi trg loại X là 9450nu nên có: 9450=X x (2^4-1)

=> nên số nu mỗi loại trong gen là

X=G= 630Nu

A=T= (1800-630x2)/2=270Nu

c) Số Nu môi trg cung cấp là

X=G=9450Nu

A=T=(27000-9450x2)/2=4050Nu

d)Số Nu mỗi loại trong từng mạch đơn là

T1=A2=90Nu

T2=A1= (270x2-90x2)/2=180Nu

G1=X2=270Nu

G2=X1=(630x2-270x2)/2=360Nu

Cho biết trình tự các nu trong mạch đơn gen:

-XGG-TAA-AXX-GTA-AXA-AG...

a, Xác định trình tự các loại aa mã hóa trong mạch đơn đó của gen.

b, Do phóng xạ làm mất nu số 6 ra khỏi gen. Xác định trình tự aa mã hóa trên gen đột biến biết:

GTA:Histidin          TAA:Izoloxin          AXX:Triptophan          XXG:Glixin          XGG:Alanin          AXA:Xistain          AAX:Loxin          XAA:Valin          XTA:Axit Aspatic

1 gen có chiều dài 2040 \(A^0\) sao mã 1 lần, mARN có 2 riboxom trượt qua không lặp lại. Xác định số aa cần cung cấp cho quá trình tổng hợp pr, số liên kết peptit hình thành khi tổng hợp nên 1 phân tử pr nói trên.

Trong nhân 1 tế bào xét 3 gen A, B, C có chiều dài bằng nhau, cùng nằm trên 1 NST.

- Gen A có tổng số liên kết Hidro bằng 1900.

- Gen B có số lượng A nhiều hơn số A gen A là 80 nu, ít hơn số gen C 10 nu loại A. Khi tế bào chứa 3 gen trên nguyên phân 1 số lần liên tiếp thì môi trường nội bào đã cung cấp cho sự tự nhân đôi 3 gen là 67500 nu các loại.

a, Tính số lần nguyên phân tế bào.

b, Tính chiều dài, số lượng từng loại nu mỗi gen.

c, Khi tế bào trên đang thực hiện nguyên phân, người ta thấy có tổng số 768 gen trong tế bào. Xác định số lần nguyên phân tế bào.

1 gen có chiều dài 0,255 micromet, có hiệu số nu loại T với 1 loại nu không bổ sung là 30% số nu gen. ARN thông tin tổng hợp từ gen đó có U = 60% số rnu. Trên 1 mạch đơn gen có G = 14% số nu mạch, A = 450 nu.

1. Số lượng từng loại nu gen, từng mạch đơn gen.

2. Số lượng, tỉ lệ % từng loại rnu.

3. Số lượng aa cần cung cấp cho quá trình tổng hợp pr nếu cho rằng gen sao mã 4 lần, trung bình mỗi mã sao có 8 riboxom trượt không lặp lại.