a. in the morning at nine/on June first,1968 b. on June first,1968/in the morning at nine

b. at nine in the morning/on June first,1968 d. on June first,1968/at nine in the morning

12.Three-fourths of the surface of the earth ______ covered with water.

a. are b. is c. were d. be

13.This month the production of stainless steel in our steelworks has increased ______ 2,000 tons.

a. with b. in c. on d. by

14.With the miniaturization of the structural components the weight of these electric devices has decreased ________ 30 percent.

a. as b. with c. in d. by

15.The Olympic Games are held ______.

a. every four years b. every four year c. every fourth years d. every four-years

16.As he is not in good health, he goes to his factory only ______ just to learn something about the progress of experiment.

a. once a week b. one week c. one time a week d. one a week

17.Three students ______ in this university come from the South.

a. of ten b. out of in ten c. out of ten d. in ten

18.Strings of the same thickness made of nylon are ______.

a. five times stronger than those b. five time stronger than those

b. five times strong than those d. five times stronger as those

19.the wheels of the old wagon are nearly ______ those of a modern car.

a. twice the size of b. twice size of c. twice sizes of d. twice the size of

20.One day on the moon is ______.

a. two Earth week long b. two Earth weeks long

b. two Earth weeks longer d. two Earth weeks length