题目内容：

    You can’t see it with your own eyes，but your smart-phone is likely to be covered with bacteria- perhaps even more so than your toilet seat. That's a lot of dangerous microbes（微生物）floating around, and yes, it is terribly dirty.

In this age of global travel and trade, it’s more important than ever to cut down on possible routes of infection and to stop bacteria and viruses spreading from person to person. Part of that means making sure your phone isn’t sending anything more than data.

And besides the potential health risks of a dirty phone, there's also the simple annoyance of looking at a screen that’s covered in fingerprints and other oily spots that are part of life with a smart-phone.

In short, you’ve got plenty of reasons to regularly give your phone a thorough clean. Not just during a pandemic（大流行病），either-we should be thinking about keeping our phones bacteria free all the time, says microbiologist Paul Turner, a professor at Yale University.

After all, we touch our phones all the time and many of us are relatively careless about cleaning them. “It sets the stage for kind of concern,” Turner says. “People could be handling phones and picking up any bacteria or virus that can attach to a surface and survive for a period of time.”

Take SARS-CoV-2, the corona- virus（冠状病毒）that causes the COVID-19, for example. Scientists are still trying to get solid evidence, but early research suggests that it can survive on plastic or stainless steel（不锈钢）surfaces for two or three days. That means you could be washing your hands perfectly well, but immediately picking the virus up again as soon as you reach for your phone.

You could be doing everything right（like washing your hands and staying away from people），but

if there’s a contaminated surface in your home or your pocket, you could expose yourself to the virus anyway, Turner says.

1.Why does the author mention the toilet seat?

A.To draw a vivid picture of a dirty phone.

B.To show how dirty a toilet seat is.

C.To add some background information.

D.To introduce a topic for discussion.

2.What can we learn in Paragraph 6?

A.Simply washing our hands is not enough.

B.Scientists have got solid evidence of the COVID-19.

C.The corona-virus can survive on smooth surfaces for 2 or 3 weeks.

D.The author suggests washing our hands before using our phones.

3.What do the underlined words “contaminated surface” refer to in the last paragraph?

A.A stainless steel. B.A deadly virus.

C.A clean phone. D.An infectious phone.

4.What is the main idea of the text?

A.You may get infected with your dirty phone.

B.You are supposed to wash your hands.

C.You’d better clean your dirty phone.

D.You’d better throw away your dirty phone.