44. The reason for Pluto's departure is that ____________.

　　 A. Pluto does not fit the definition of a "planet"

B. Pluto cannot compete with other planets

　　 C. Pluto is attracted by Neptune's gravity

　　 D. other objects of its size have been discovered

43. Scientists argued about Pluto's status for a long time because _____________.

　　 A. Pluto was first discovered in 1930

　　 B. the family of planets is too big

　　 C. Pluto is located beyond Neptune

　　 D. many dwarf planets, like Pluto, were found

42. We can infer from the text that _____________.

　 A. eight planets make up the solar system

　 B. it has been hard for scientists to define a "planet"

　 C. Mars is very hot and you can't go near it

　 D. Pluto shares the same orbit with Neptune

41. The main purpose of the text is to ____________.

　 A. prove to the readers that size matters

　 B. tell readers about a big change of the planets

　 C. explain the classical theory of planets

　 D. inform us of science textbooks being updated

39.　 if,表假设关系。

38．that，考查so．．．that…的结构。

37．No, No one is allowed to leave．．．表任何人不允许离开……。

36．more，从前文可知此处表更进一步了解产。

35．after．表“我的介绍之后，今天上午的其他安排。