Unit 3 Computers 同步练习 1-20（略） 阅读下列短文，从每题所给的四个选项（A、B、C、和D）中，选出最佳选项，并在答题卡上将该项涂黑。 A The Healthy Habits Survey(调查)shows that only about one third of American seniors have correct habits. Here are some findings and expert advice.21教育网 1．How many times did you brush your teeth yesterday?21·世纪*教育网 Finding：A full 33% of seniors brush their teeth only once a day. Step：Remove the 300 types of bacteria in your mouth each morning with a battery operated toothbrush. Brush gently for 2 minutes, at least twice a day. 2．How many times did you wash your hands or bathe yesterday? Finding：Seniors, on average, bathe fewer than 3 days a week. And nearly 30%wash their hands only 4 times a day—half of the number doctors recommend. Step：We touch our faces around 3,000 times a day－often inviting germs(病菌)to enter our mouth, nose, and eyes. Use toilet paper to avoid touching the door handle. And, most important, wash your hands often with hot running water and soap for 20 seconds. 3．How often do you think about fighting germs? Finding：Seniors are not fighting germs as well as they should. Step：Be aware of germs. Do you know it is not your toilet but your kitchen sponge(海绵)that can carry more germs than anything else? To kill these germs, keep your sponge in the microwave for 10 seconds.21*cnjy*com 21．What is found out about American seniors? A．Most of them have good habits. B．Nearly 30%of them bathe three days a week. C．All of them are fighting germs better than expected.【来源：21cnj*y.co*m】 D．About one third of them brush their teeth only once a day.21教育名师原创作品 22．Doctors suggest that people should wash their hands_____. A．twice a day B．three times a day C．four times a day D．eight times a day 23.Which of the following is true according to the text? A．We should keep from touching our faces. B．There are less than 300 types of bacteria in the mouth. C．A kitchen sponge can carry more germs than a toilet. D．We should wash our hands before touching a door handle.21*cnjy*com 24．The text probably comes from_____. A．a guide book B．a popular magazine C．a book review D．an official document B A computer virus is a computer program that is written by a malicious (怀有恶意的) author. They spread by copying themselves, then transferring onto other computers. There are around 53,000 computer viruses in existence, with a new one detected every 18 seconds. A computer virus can do everything, from popping up a short message to wiping key files, so that your computer doesn’t work. The “I LOVE YOU” virus infected up to 45 million computers, causing ￡7 billion worth of damage worldwide. How to avoid catching a virus? Stay calm. A computer virus isn’t dangerous until the infected e-mail is opened. Deleted items folder. Don’t open any attachment (附件) you are not sure about, even if you have a virus scanner . Read the e-mail and check that the contents of the message make sense befor ... ...
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