问题 选择题

2013年10月8日,郑州市区被大雾笼罩,空气严重污染,其首要污染物为PM2.5。PM2.5是指大气中直径小于或等于2.5×10-6m的颗粒物,又称可入肺颗粒物。下列有关说法不正确的是

A.雾是由大量悬浮在近地面空气中的微小水滴或冰晶组成的气溶胶,多出现于秋冬季

B.焚烧秸秆和化石燃料的燃烧会增大空气中PM2.5的含量

C.PM2.5在空气中一定能产生丁达尔现象

D.开发利用新能源,实施“低碳经济”,可减少PM2.5的产生

答案

答案:C

题目分析:分散系的分散质粒子大小在1-100nm为胶体,故PM2.5在空气中一定能产生丁达尔现象,C错误。

阅读理解

阅读理解。

     One day, a teacher was giving a speech to his students. He held up (举起) a glass of water and asked the

class, "How heavy do you think this glass of water is?"

     The students' answers ranged from 20 g to 500 g? "It does not matter on the weight itself. It depends on

how long you hold it. If I hold it for a minute, it is OK. If I hold it for an hour, I will have an ache in my right

arm. If I hold it for a day, you will have to call an ambulance (救护车). It is exactly the same weight, but the

longer I hold it, the heavier it becomes."

     If we carry our burdens (负担) all the time, sooner or later, we will not be able to carry on, the burden

becoming increasingly heavier.

     "What you have to do is to put the glass down, rest for a while before holding it up again."

     We have to put down the burden sometimes, so that we can be refreshed and are able to carry on.

     So before you return home from work tonight, put the burden of work down. Don't carry it back home.

You can pick it up tomorrow.

     Whatever burdens you are having now on your shoulders, let it down for a moment if you can.

1. The teacher brought a glass of water to the class because _____. 

A. he was very thirsty

B. his arms were strong

C. it was a good example

2. "A glass of water" in this passage referred to (指) _____.

A. knowledge

B. the burden

C. the time 

3. According to the teacher, you may feel _____ if you put down the burden sometimes.

A. more energetic

B. much heavier

C. more stressed out

4. This was a lesson about _____.

A. how to relax oneself in life

B. how to solve a physics problem

C. how to keep fit by drinking water

5. Which of the following statements is TRUE according to the passage?

A. You could become heavier and heavier if you held a glass of water in your hand.

B. All the students in the class knew what the weight of the glass of water exactly was.

C. The teacher had a good way of making his lesson clear and easy to be understood

单项选择题