Cho hình chóp tứ giác đều S.ABCD có tất cả các cạnh đều bằng a. Bán kính của mặt cầu ngoại tiếp hình chóp nói trên bằng:           

Choose the best answer for the following sentence:

''How are you feeling?'' ''I' ve been feeling better since ________________.''

Choose the best answer for the following sentence:

''Isn't it hard to drive downtown to work?'' ''Yes, that's why I ___________________ to work by train.''
 

Choose the best answer for the following sentence:

''How long have you been with the company?'' ''I there for two
years by January.''
 

Choose the best answer for the following sentence:

''When are you planning to send the memo to the staff?'' ''I ________________ it already.''

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

        A species that faces overexploitation is one (1)___________ may become severely
endangered or even extinct due to the (2)________ in which the species is being used.
Unrestricted whaling during the 20th century is an example of overexploitation, and
the whaling (3)_________ brought many species of whales to extremely low (4)_______ 
sizes. When several whale species were nearly extinct, a (5)____________ of nations
agreed to abide by an international moratorium on whaling. Due to this moratorium,some whale species, such as the grey whale, have (6)________ remarkable comebacks, while others (7)___________ threatened or endangered.
           Due to the (8)_______ in animal parts, many species continue to suffer high
rates of exploitation. Even today, there are (9)_______ for items such as rhino horns and
tiger bones in several areas of Asia. It is here that there exists a strong market (10)____ traditional medicines made from these animal parts.

1. A. that                B. who                  C. whom                  D. where
2. A. measure         B. speed               C. rate                     D. ratio
3. A. company        B. employment      C. agency                 D. industry
4. A. people           B. population         C. humanity             D. mankind
5. A. total              B. number              C. sum                     D. crowd
6. A. made             B.done                  C. opened                D. produced
7. A. prepared       B. waited               C. remain                 D. come
8. A. purchase       B. agreement        C. exchange             D. trade
9. A. requirement  B. suggestions      C. demands              D. wishes
10. A. with            B. of                       C. at                         D. for

Choose the best answer for the following sentence:

''Mary told me that you have a cottage on Lake Superior.'' ''Yes, we __________________ there since we first moved to Michigan.''
 

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

                Our family has got many books. All the (1)___________ of our family buy books
and read them. My mother says that books help us in self-education. In ancient times books (2)_______ written by hand. It was difficult to write a book (3)_______ a pen. Then printing came into our life. Printing played an important (4)_______ in the development of literature and culture. Now there are a lot of books in the shops, there are many books in our flats. But it is difficult to buy all books (5)______we want to read. That's why we get books in public libraries. There are some problems in our life and sometimes it is difficult to (6)_________ them. I think that books can help us. Last year I read a very interesting book "An American Tragedy" by Theodore Dreiser. 
        This novel was (7)______ at the beginning of the 20th century. The novel (8)_____ the tragic fate of a boy and a girl, Clyde and Roberta (9)_______ name. It is a sad story. This novel was written many years ago, but it is (10)______ nowadays. Books must be our friends during all our life.

1. A. members                B. partners                C. groups                 D. relates
2. A. are                         B. were                      C. have                    D. had
3. A. in                            B. by                          C. with                     D. at
4. A. step                        B. stage                    C. chain                    D. role
5. A. who                        B. which                     C. when                   D. where
6. A. deal                        B. imagine                 C. create                   D. solve
7. A. published               B. presented             C. opened                 D. constructed
8. A. writes                    B. prescribes              C. describes              D. mentions
9. A. on                          B. by                          C. of                          D. with
10. A. amazing               B. favorite                  C. popular                D. worth

Choose the best answer for the following sentence:

''Where are Ken and Janet?'' ''They were hungry, so they ___________________ to the grocery store.''

Choose the best answer for the following sentence:

'' ______________ lunch already?'' ''No, not yet. The waitress ________________ my order
fifteen minutes ago and __________________  me anything yet.''

Choose the best answer for the following sentence:

I ___________________ to get into contact with them for a long time, but now I _______________ it up as hopeless.