题干

生物体内含Zn2+的酶最多,有70多种酶的活性与Zn2+有关,缺乏Zn2+生物就无法正常生活,这说明无机盐(   )

A:对维持细胞形态有重要作用

B:对维持生物体的生命活动有重要作用

C:对维持酸碱平衡有重要作用

D:对调节细胞内的浓度有重要作用

上一题 下一题 0.0难度 选择题 更新时间:2019-10-31 04:46:14

答案(点此获取答案解析)

B

同类题2

阅读短文,回答问题。

                                                                                                          白杨树

白杨树是西北最普通的一种树,只要有草的地方,就有白杨树的影子。

白杨树是不太讲究生存条件的,大路边,田埂旁,哪里有黄土的地方,哪里就有她的生存。她不追逐雨水,不贪恋阳光,只要能够在哪怕板结的土地上,给一点水分,白杨树的一截枝条就会生根,抽芽。只要挪动一点杂草生存的空间,她就会把黄土地装点,撑起一片绿色。她不需要人去施肥,也不需要像娇嫩的草坪那样去浇灌。只要不挥刀斧去砍伐,给她一点宽松的环境,让她吸收自由的空气,她就会挺拔向上,她从来不对生长的土地说不。她不枝不蔓,扎根在贫瘠的土壤中,随遇而安,与世无争,因为她属于草根族。

白杨树虽然出身寒微,却是最讲究生存质量的。土壤里还透着冰碴,春风中还夹着寒意,她的枝头已经冒出翠绿的嫩芽,在沉重的压力下,她的每一个嫩芽,每一片叶子都是努力向上的,而绝不弯腰乞求,更没有媚俗的面孔。

秋风里,虽然脱尽了叶子,单薄的枝条依然透着精气,枝干向上,高昂着头。严冬里,她迎着刀霜雪剑,依然伫立在寒冷的黄土地。白杨树并没有想到移栽和迁徒,哪怕她的残落枝叶腐化归于泥土,也要为这黄土地增添一点养分和活力。厚实的黄土地下,涌动着白杨树不朽的生命,黄土地酥酥地勃发了,一片片地延伸着绿。

同类题4

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    Taking good notes is a time-saving skill that will help you to become a better student in several ways. ____ Second, your notes are excellent materials to refer to when you are studying for a test. Third, note-taking offers variety to your study time and helps you to hold your interest.

    You will want to take notes during classroom discussions and while reading a textbook or doing research for a report. ____ Whenever or however you take notes, keep in mind that note-taking is a selective process. ____

The following methods may work best for you.

●Read the text quickly to find the main facts and ideas in it.

●Carefully read the text and watch for words that can show main points and supporting facts.

●Write your notes in your own words.

____

●Note any questions or ideas you may have about what was said or written.

    As you take notes, you may want to use your own shorthand(速记). When you do, be sure that you understand your symbols and that you use them all the time. ____

A. Use words, not complete sentences.

B. There are three practical note-taking methods.

C. You must write your notes on separate paper.

D. Otherwise, you may not be able to read your notes later.

E. You will also want to develop your own method for taking notes.

F. That means you must first decide what is important enough to include in your notes.

G. First, the simple act of writing something down makes it easier for you to understand and remember it.