单项选择题：液相色谱流动相过滤必须使用过滤膜的粒径是（） A.0.5μm B.0.45μm C.

题型：单项选择题

第二节完形填空 (共10小题，每小题2分，满分20分)

阅读下面短文，掌握其大意，然后从41—50各小题所给的A、B、C和D项中，选出最佳选项，并在答题卡上将该项涂黑。

Life on Land probably began about 430 millions years ago, though it has existed in the water for perhaps as much as 3,000 million years. When we think of the first thing on land, we probably think of strange ___41___coming out of the oceans, but in fact no animals could have been _42__ if plants had not been on land first. Plants had to be on land before animals arrived. They __43___ the first land animals with the surrounding and food necessity, since they, the plants are the only form of life that is able to get and store__44__.

The first plants to exist out of water were probably __45__ kinds of algae(海藻) which were __46__ by other plants that grow ___47__ to the ground and needed water in which to reproduce. Once the move to land had been made, however, evolution (进化) took place quickly. By the end of 100 million years, plants had developed their __48__, and some had got tree-like forms since height was very important in gaining __49__. About 30 million years ago, much of the world was covered with forests of huge trees. In most ways they were like _ 50__ modern trees. They had roots, leaves, wood, but mostly they had not developed

seeds.

41. A. tree B. plants C. seeds D. animals

42. A. living B. making C. dying D. eating

43. A. offered B. supplied C. gave D. afforded

44. A. heat B. sunlight C. energy D. water

45. A. many B. little C. sure D. certain

46. A. followed B. made C. copied D. existed

47. A. close B. far C. strong D. tall

48. A. branches B. trunks C. roots D. leaves

49. A. weight B. sunlight C. soil D. water

50. A. modern B. ancient C. big D. small

查看答案

液相色谱流动相过滤必须使用过滤膜的粒径是（） A.0.5μm B.0.45μm C.

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