Ở ruồi giấm, gen A quy định tính trạng mắt đỏ, gen a đột biến quy định tính trạng mắt trắng. Khi 2 gen nói trên tự tái bản 4 lần thì số nuclêôtit trong các gen mắt đỏ ít hơn các gen mắt trắng 32 nuclêôtit tự do và gen mắt trắng tăng lên 3 liên kết hiđrô. Hãy xác định kiểu biến đổi có thể xảy ra trong gen đột biến?

Choose the best answer for the following sentence:

Had Ramon got to the station on time, he ___________ the train

Choose the best answer for the following sentence:

She ___________ the news if she ______________ the radio this morning.

Choose the best answer for the following sentence:

I _____________ the contract unless you ___________ to it.

Choose the best answer for the following sentence:

The first year at college was probably the most ___________ year of my life.

Choose the best answer for the following sentence:

 No one seemed to notice my ____________ and I felt so lonely.

Choose the best answer for the following sentence:

My roommates __________ my having a light on while she was trying to sleep. 

Read the following passage and choose the best answer for each blank: 

          Students who attend the Scottish Universities can do an ordinary degree in three years, (1)_________ complete an honour degree in four years. There are also sandwich courses in (2)_________  the student may need to do a year more. The sandwich courses (3) ___ work placement which (4)_____ the students to work for a short period of time before they complete their courses. Scottish universities tend not to specialise subjects (5)____ the third year when students may decide to complete an ordinary degree in a (6) ______ year or embark on a two-year honour course. Most universities award a Bachelor Degree to the students who have completed their undergraduate courses (7)________  for historical reasons, the Scottish ancient universities award a Master of Arts (MA) degree to arts students who have completed their undergraduate courses. These MA degrees are (8)________ to a Bachelor Degree. Honour degrees are usually split into classes: first class (I), upper second class (II :1), lower second class (II :2) and third (III), and unclassified (below third class). Students who apply (9)______ a Scottish University while attending a Scottish secondary school (10)_______ not need to pay for university tuition fees as it is paid for on their behalf by the Student Awards Agency for Scotland.

1. A. and              B. nor                 C. or                D. either
2. A. which           B. that                C. where.        D. whom
3. A. invite           B. please            C. offer            D. display
4. A. lets              B. opens             C. allows.        D. suggests .
5. A. once            B. until                C. after            D. soon
6. A. further         B. farther            C. better          D. higher
7. A. despite        B. in spite           C. but               D. though
8. A. equivalent    B. same             C. familiar          D. comparative
9. A. to                B. for                  C. in                  D. with
10. A. are            'B. may               C. do                 D. must

Read the passage below and choose one correct answer for each question:

             A change in the federal regulations now requires that every international student admitted to the United States on an F-1 visa be assigned a social security number. The record will be marked to indicate that it is a non-work number and may not be used for off-campus employment purposes. If the number is ever used in a job, the Social Security Office will notify the Immigration and Naturalization Service (INS). Unless prior work permission has been granted by INS, the student may be asked to depart the country. Students who wish to work on campus may do so without notifying INS.

1. The title below that best expresses the ideas in this passage is __________ .            A. Invitation              B. Notice                C. Questionaire              D. Application

2. Why are international students assigned social security numbers?
A. Because they need in order to work off campus.
B. Because they need them in order to depart the United States.
C. Because they are required to have them in compliance with federal regulations.
D. Because they need them in order to be granted F-1 status.

3. All of the following are true concerning a social security number for international students EXCEPT ___________ .
A. It is a non-work number.
B. It may not be used for off-campus employment.
C. It is assigned only to students who want to work on campus.
D. It is used by students with F-1 visas.

4. In line 1, the word “regulations” is closest in meaning to________ .
A. laws            B. governments                  C. employees               D. offices

5. Evidently, an international student can work without receiving permission from INS _________ .
  A. at the Social Security Office                    B. at State University library                            C. nowhere                                                 D. at the city airport

Choose the best answer for the following sentence:

If I can't do my homework this afternoon, ____________ .

Choose the best answer for the following sentence:

If you travelled by plane, ____________ .