问题 单项选择题

用溶液吸收管采样时,为防止水雾进入转子流量计,应采取什么措施()

A.降低流量减少水雾

B.在吸收液中加表面活性剂

C.降低采样温度

D.在吸收管出口与流量计之间装一只阻力小的除水管

E.在吸收管入口加过滤装置

答案

参考答案:E

解析:在使用转子流量计时,若空气中湿度太大,需要在转子流量计进气口前连接干燥管,否则转子吸附水分后增重,影响测量结果。

单项选择题
阅读理解

Working hard for fun

No more pencils! No more books

No more teacher’s serious looks!

After a long period of study and work, the young Americans burst through the school doors singing.

But unfortunately, American students do very poorly and are among the worst students in the world. In the entire field of subjects---from geography and maths to science and general knowledge. American students are the poorest performers. Why? What’s the reason behind the scene? One problem lies in the fact that so little is expected from them. The standards of success are too low. Teachers are not willing to give out low grades and fail students. Besides, the existing negative results are few and mean little to students if their performance in study is poor . Of course some students realize that a high school diploma is a measure of success and will be important to get a job or get admitted into college. But they only have to go through the motions without really trying. They learn to get by with a minimum of effort.

In America, it is simply too easy for high school students to enter college. This forms a sharp contrast with the students in China and other Asian countries who have to suffer heavy pressure from parents, teachers and cruel social facts. Chinese students have to study hard for long years to pass the national college entrance examination which few Americans will take such trouble to enter to university. The majority American students know that they will be able to get into some college, so they do not really worry about it.

It turns out that American high school students are just too busy to find time to study. They spend almost no time on study while students from other countries spend four or five hours per day on homework. American students on the average give less than five hours per week to their studies. Learning and reading for future are not important to them. Many American never read. It is little wonder why Americans knows less than students from other countries.

1. Why are American students the poorest performers in the entire field of subjects?

A. Because they are too busy to find time to study.

B. Because they are too stupid and too lazy.

C. Because they care little about their study.

D. Because so little is required from them

2. Which of the following is Not true ?

A. Most of American students spend less than five hours on their study every week.

B. Few American students have trouble to enter college.

C. American students can be admitted into college even without a high school diploma.

D. It is hard for the students in China to enter college.

3. What seems to be the writer’s attitude towards American students?

A. He probably thinks much should be expected from them.

B. He is in favour of American students’ learning methods.

C. He shows no interest in American students’ study.

D. He thinks American students study hard.