问题 单项选择题

相对聚氯乙烯和聚乙烯管而言,具有较高强度、较好耐热性,无毒、耐化学腐蚀,广泛应用在冷热水系统中,是最轻的热塑性塑料管,此种管材为()。

A.氯化聚氯乙烯管

B.超高分子量聚乙烯管

C.工程塑料管

D.无规共聚聚丙烯管

答案

参考答案:D

解析:本题考查的是型材、板材和管材。无规共聚聚丙烯管是最轻的热塑性塑料管,相对聚氯乙烯管、聚乙烯管来说,无规共聚聚丙烯管具有较高的强度,较好的耐热性,最高工作温度可达95℃,在1.0MPa下长期(50年)使用温度可达70℃,另外无规共聚聚丙烯管无毒、耐化学腐蚀,在常温下无任何溶剂能溶解,目前它被广泛地用在冷热水供应系统中。参见教材P28~29。

选择题
阅读理解

I began to send my first e-mail when I was 17. I discovered Google 5 years later. Now, I use the Internet all the time. Internet has become so popular that 90 percent of 12-to-17-year-olds in the United States use the Internet, according to one recent survey, and about half of those kids use it every day. They visit chat rooms and send e-mails. They go to Websites to get information for homework.

“Kids are now living in a virtual(虚拟的) world,” says Greenfield, “As the Internet is becoming more and more important for our life, we should worry about one question: Is the Internet good or bad for kids?”

“It’s X to answer the question because the Internet involves so many things,” says Justine, a media expert at Northwestern University. “They include networked computer games, news about politics, instant messaging and e-mails to your grandmother. ” So, more and more studies shows that the online world can be helpful in some ways and dangerous in others.

“Although it’s not easy to tell whether it’s good or bad,” says Justine, “the Internet, at least, is very useful and can be used widely by everyone in the world. ”

1. What percentage of American 12-to-17-year-olds use the Internet every day?

A. About 45%        B. About 50%         C. About 80%        D. About 90%

2.. Greenfield _______.

A. is an expect from Northwestern University

B. wants to stop all the kids from using the Internet

C. is worrying about whether the Internet is good or bad for kids

D. thinks that the Internet is good or bad for kids

3. “X” in the passage should be the word “_______”.

A. possible          B. difficult            C. easy             D. good

4. Which is the best title of the passage?

A. Don’t Use the Internet                        B. Kids and Emails

C. Is the Internet Good or Bad                    D. Two Experts from Universities