问题 选择题

下表是四位同学在进行显微镜观察西红柿果肉实验中所使用的镜头组合,你认为哪位同学所看到的细胞数量最少?(   )

 小丁小黄晓东李林
目镜5ⅹ10ⅹ15ⅹ5ⅹ
物镜10ⅹ40ⅹ10ⅹ40ⅹ
 

A.小丁                                 B.小黄                                 C.晓东                                 D.李林

答案

答案:B

此题主要考查显微镜的放大倍数问题。物体的放大倍数等于目镜和物镜放大倍数的乘积。显微镜的放大倍数越大,视野越暗,看到的细胞数目越少,细胞的体积越大;反之,显微镜的放大倍数越小,视野越亮,看到的细胞数目越多,细胞的体积越小。

A中,5×10=50,此镜头组合放大了50×;

B中,10×40=400,此镜头组合放大了400×;

C中,15×10=150,此镜头组合放大了150×;

D中,5×40=200,此镜头组合放大了200×。

由此可见,B选项的镜头组合放大倍数最大,则看到的细胞数目最少。故选B

填空题
完形填空

Scientists find that hard-working people can live longer than idle(不工作的) people. Career women are healthier than housewives. Evidence shows that the jobless are in poorer health than the job-holder. A report shows that whenever the unemployment rate(失业率) increases by 1%, the death rate increases by 2%. All this comes down to one point: work is helpful to health.

Why is work good for health? It is because work keeps people busy, away from loneliness. Researches show that people feel unhappy, worried when they have nothing to do. Instead, the happiest are those who are busy. Many high achievers who love their careers feel that they are happiest when they are working hard. Work serves as a bridge between man and reality(现实). By work, people come into contact with each other. By taking part in some activities, they find friendship and warmth. This is helpful to health. The loss of work means the loss of everything. It affects man in spirit and makes him easy to get ill.

Besides, work gives one a sense of fulfillment(充实感) and a sense of achievement. Work makes one feel his value in society. When a writer finishes his writing or a doctor successfully operates on a patient or a teacher sees his students grow, they are happy beyond words.

From the above we can come to the conclusion that the more you work, the happier and healthier you will be. Let us work hard and study well and live a happy and healthy life.

小题1:Who can live longer, hard-working people or idle people?

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小题2:How do people feel when they don’t have anything to do?

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小题3:How can we find friendship and warmth in our daily life?

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小题4:Why can career women be healthier than housewives? (请根据文章内容,自拟1句话作答)

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小题5:What do you think hard work can bring us? (请根据自己的想法,自拟1-2句话作答)

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