单选题 When(　　)spacecraft travels, one of the major problems is reentry into the Earth’s _______.

单选题 We cannot _______ all the magazines together.

单选题 With the help of the government,(　　)large number of people ---_______ after the flood in 1991.

单选题 This river is so big that it is impossible to build(　　)_______ under it without modern technology.

单选题 This river forms(　　)natural _______ between China and Korea.

单选题 He works in our university as(　　)visiting _______, not as(　　)formal faculty member.

单选题 She is already 16years old. But she _______as if she were still(　　)little girl.

单选题 We do not have(　　)_______ school in our institute. The highest degree we provide for the students is(　　)B.A. and(　　)B.S..