问题 选择题

观察细胞常用显微镜,用下列四台显微镜观察洋葱表皮细胞,视野中细胞数目最多的显微镜是哪一台(  )

A.1

B.2

C.3

D.4

答案

显微镜的放大倍数越大,视野就越小,看到的细胞就越大,但数目最少;显微镜的放大倍数越小,视野就越大,看到的细胞就越小,但数目最多;显微镜的放大倍数的计算是目镜的放大倍数乘以物镜的放大倍数.在四个选项中A选项放大40倍,B选项放大400倍,C选项放大了150倍,D选项放大300倍,只有A选项的1号显微镜放大倍数最小,所以看到的细胞最小数目最多.

故选:A

阅读理解

Who is reading your blogs or checking out your information online? Two reports show that surfing the Internet and sending personal information to people you do not know could be a problem.

Most sites give users their own webspace where they can write their diaries or post their pictures. The sites encourage users to get their friends to look at their work and to comment(评论)on what are posted on the sites.

Teachers are worried that some children are posting their personal information on websites. This could put them at risk from those who plan to do harm to young people. Teachers are also worried some users think it is OK to use the websites in a way that could get others into trouble.

In a school in Illinois(伊利诺斯州)in the US where some popular sites are used wildly, the school would punish(惩罚)students who posted pictures or information about smoking , drinking and other illegal(违法的)activities on the websites.

The school is now going to encourage its 3,200 students to obey a new rule. The warning is clear. That is, be careful when posting information about yourself such as your age, sex, address and interests on a website that anyone can see.

Another warning about the Internet comes from a report. It shows searchers are leading users to websites that show them spam(垃圾短信)and other dangerous downloads.The words “ free screen savers” were found to be the most dangerous words that people search for.

It is well-known that visiting sites offering free MP3s leave users at serious risk. Spyware(监控软件)should be installed on their computers. So, happy surfing ,but remember not to get caught in the Net!

小题1:What kinds of pictures or information are not allowed on the websites in a school in Illinois?

A.Smoking , drinking and exercising.

B.Drinking, fighting and playing.

C.Smoking, drinking and fighting.

D.Chatting, watching and smoking.小题2:What does the underlined phrase “screen savers” in the sixth paragraph mean?

A.The program of hurting screens.

B.The program of protecting screens

C.The program of using screens less.

D.The person who uses screens less.小题3:How do the users avoid the danger of downloading information?

A.By using spyware.

B.By not going online.

C.By getting others into trouble.

D.By being happy.小题4:What’s the best title of this passage?

A.Happy but safe surfing.

B.Don’t comment on the Internet.

C.Warning about downloads.

D.Activities on the websites.

单项选择题