题干

下表中各元素的数据代表该元素占原子总量的百分比.请据表回答问题.

岩石的

成分%

其他成分<0.1

47

28

7.9

4.5

3.5

25

2.5

2.2

0.46

0.22

0.19

人体的

成分%

其他成分<0.1

63

25.5

9.5

1.4

0.31

0.22

0.03

0.06

0.05

0.03

0.01

(1)组成人体的化学元素在元素周期表上都有,它普遍存在于非生物界,生物体内不包含特殊的“生命元素”,这个事实说明____ 

(2)生物从非生物环境中获得的元素与环境中的元素的比例相差甚远.如岩石圈中氢、碳、氮加在一起占总原子数不到1%,而在生物体中则占74%左右.这个事实说明____ .

(3)从此表看,人体成分中没有铁的含量,是否人体不含铁?____.为什么?____

(4)人体内的镁可以从蔬菜中的什么器官获得?____.为什么?____ .

(5)在上述元素中,人体核酸是由____ 元素组成.

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同类题4

阅读理解

    That cold January night, I was growing sick of my life in San Francisco. There I was, walking home at one in the morning after a tiring practice at the theatre. With opening night only a week away, I was still learning my lines. I was having trouble dealing with my part-time job at the bank and my acting at night at the same time. As I walked, I thought seriously about giving up both acting and San Francisco. City life had become too much for me.

    As I walked down empty streets under tall buildings, I felt very small and cold. I began running, both to keep warm and to keep away from any possible robbers (抢劫犯). Very few people were still out except a few sad-looking homeless people under blankets.

    About a block from my apartment (公寓房间), I heard a sound behind me. I turned quickly, half expecting to see someone with a knife or a gun. The street was empty. All I saw was a shining street-light. Still, the noise had made me nervous, so I started to run faster. Not until I reached my apartment building and unlocked the door did I realize what the noise had been. It had been my wallet falling to the street.

    Suddenly I wasn't cold or tired any more, and I ran out of the door and back to where I'd heard the noise. Although I searched the street anxiously for fifteen minutes, my wallet was nowhere to be found.

    Just as I was about to give up the search, I heard the garbage truck (垃圾车) pull up to the street next to me. When a voice called from the inside, "Alisa Camacho?" I thought I was dreaming. How could this man know my name? The door opened, and out jumped a small red-haired man with an amused look in his eyes.

    "Is this what you're looking for?" he asked, holding up a small square shape.

    It was nearly 3 a.m. by the time I got into bed. I wouldn't get much sleep that night, but I had got my wallet back. I also had got back some enjoyment of city life. I realized that the city couldn't be a bad place as long as people were willing to help each other.