问题 选择题

在使用显微镜时,用于调节光线强弱的结构是                  (      )

A.物镜

B.转换器

C.遮光器

D.准焦螺旋

答案

答案:C

题目分析:在使用显微镜时,用于调节光线强弱的结构有两个,分别是遮光器和反光镜。遮光器上有大小不同的光圈,反光镜一面是平面镜,另一面是凹面镜,当环境光线强时应使用小光圈、平面镜;当环境光线暗时,应使用大光圈、凹面镜,选C

单项选择题
单项选择题

Are you going to high school to go on with your study What will you do if you can’t Don’t worry. Vocational schools are open for you because our country is in need of people with special skills.

Compared with common high schools, vocational schools have more advantages. Firstly, in order to promote the development of vocational education, our country spends a lot of money on it. So you need to pay only a smaller half of the school fee. Secondly, in here you have already started learning practical skills that you can use all your life. But some other students may still worry about how to spend the long three years at high schools. Why Because they didn’t choose the school that suits them. And finally, when they are still wondering where to go, you are already able to live on your own hands proudly. And perhaps it won’t be long before you are on the road to success.

People take different roads because they have different potentials. So different students should choose different schools. Go to high school if you think that you can go farther on that road. Choose a key high school if you are lucky enough to have the chance. Enter a vocational school if you are interested in the lessons there and you are better at making things with your hands.

In a word, think carefully and see what kind of person you are. Remember, always choose things that suit you.

This passage is written to ().

A.advise some students to choose vocational schools

B.talk about the advantages of common high schools

C.discuss how to divide students into different groups

D.compare different schools