选择萃取剂将碘水中的碘萃取出来，这种萃取剂应具备的性质是 [ ] A．不溶于水，
题型：不定项选择题
问题：
选择萃取剂将碘水中的碘萃取出来，这种萃取剂应具备的性质是 [ ]
A．不溶于水，且必须不与碘发生化学反应
B．不溶于水，且比水更容易使碘溶解
C．不溶于水，且必须比水密谋大
D．不溶于水，且必须比水密度小
题型：不定项选择题
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