Your smartphone(智能手机) can do a lot of things. It can call people. It connects to the Internet. It enables you to play fun games. But there is a dark side to this smart little device（设备）of yours – it might also spread disease.
“People are just as likely to get sick from their phones as from handles of the bathroom,” Jeffrey Cain, the president of the American Academy of Family Physicians, told The Wall Street Journal.
This may be hard to believe, but scientists reached this conclusion after they tested eight random cell phones from an office in Chicago. All the tested phones showed high numbers of coliforms(大肠菌), a kind of bacteria found in excrement(粪便)，with about 2,700 to 4,200 units of the bacteria on each phone. In drinking water, the healthy limit is less than 1 unit per 100 ml of water. This bacteria can cause flu, pinkeye（红眼病）and diarrhea(腹泻).
Although computers, keys and pens all carry germs(细菌), our smartphones get far dirtier. They touch a lot of stuff, including our hands and the inside of our pocket or purse. We take them almost everywhere: the bus, the subway and who hasn’t played Angry Birds of Fruit Ninja while sitting on the toilet?
“Some things that we think are personal are actually more public than we imagine,” Cain said.
What’s even worse is that after the phone returns from its dirty trip, it then spends most of its time cozying up to our faces. You don’t think about how often you touch your phone to your face, do you? Our noses, mouths and ears are all warm and rich in grease（油脂）, an environment that germs really like.
Compared to traditional keypads（键盘）, touch screens transmit（传播）germs more easily to hands. According to Time magazine’s website, an expert in Australia warned that playing with iPads and iPhones at Apple stores is a health risk.
So how do you keep your smartphone clean? Alcohol is effective when used to kill germs from the back and side of your phone. But it might harm the screen. There is one simple and reliable way you can reduce the germs on your phone’s surface: wash your hands regularly.
The underlined word “dark” in the first paragraph means       .

A．black	B．hopeless
C．unclear	D．unpleasant

By saying “Some things we think are personal are actually more public than we imagine”, Cain meant that         .

A．people love to share their smartphones more than they realize

B．our personal items could be as risky to our health as public items

C．smartphones are used in public places more than people realize

D．most people don’t know how dirty their cell phones are

Compared with traditional keypads, smartphones         .

A．make contact with our hands more often

B．are greasier and need more alcohol to clean

C．get warm more easily and are harder to clean

D．get much nearer to our faces

What is the article mainly about?

A．Tips on the use of smartphones.

B．Health problems caused by the use of smartphones.

C．The danger of coliforms infection.

D．The influence that smartphones have on our life.