【单选题】They are signing shorter contracts, too. But still, they need to think harder about what is their core business, and what is _________.

Heredity(遗传) is not the only thing that influences our color. Where we live and how we live after we are born are important too. For instance, our genes influence how fat or thin we are. But our weight depends mainly upon how much we eat and how much exercise we get. In the same way, our skin color depends to a large extent upon how much sunshine we get.

When summer arrives and light—colored people go to the beaches, some will tan darkly, some will tan lightly and few will not tan at all. Each one has inherited a different ability to tan, but the differences do not appear until the conditions are right. An outdoor man will soon become pale if he changes to an indoor job, while a desk clerk will take on tan after a short vacation in the sun.

Sometimes people decide that being tanned is better than being pale. Sometimes they decide the opposite.

Centuries ago, most of the people in Europe were peasants and they had to work in the fields all day. Noblemen, on the other hand, did not have to work. They stayed indoors and remained pale. You could always tell a nobleman from a peasant because a peasant had a tan. As a result, a shin so pale that the veins (血管) showed was considered a mark of great beauty.

During the Industrial Revolution things changed. Farmers left their fields and went to work in factories, mines and mills. Working for long hours in dimly—lit factories and mines made their skins pale. (77) Wealthy people, however, could afford to travel so sunny countries. They had the leisure to lie around on the beaches and get tan. Having a tan became a sign of wealth.

In Western Europe and North America pale skin is no longer desirable. Instead of bleaching themselves white with lemon juice, many women spend their time under a sun—lamp. The desire for a quick tan has led to the invention of pills and lotions (涂剂) that darken the skin artificially without exposure to sunlight. These pills and lotions can be bought by anyone at any drugstore. A rich man can spend hundreds of dollars on a vacation in the sunny West Indies and get his suntan there. But his lowest—paid clerk can have what looks like the same tan out of a bottle for a few cents.

Besides genes, our skin color has much to do with ______.

A．exercise

B．weight

C．food

D．sunshine

What happen to the universities and colleges?

A．They are reluctant to change.

B．They follow the traditional way of teaching.

C．They empower students as education consumers.

D．They need to concentrate on the student's needs.

According to the passage, people are stressed because they fail to think ahead of the next task.

A．YES

B．NO

Sleep is a funny thing. We're taught that we should get seven or eight hours a night, but a lot of us get by just fine on less, and some of us actually sleep too much. A study out of the University of Buffalo reported that people who routinely sleep more than eight hours a day and are still tired are nearly three times as likely to die of stroke--probably as a result of an underlying disorder that keeps them from sleeping soundly.

Doctors have their own special sleep problems. Residents are famously short of sleep. It is not unusual for. them to work 40 hours in a row without rest. They are not in the least worried about it, confident they can still deliver the highest quality of medical care. But an article in the Journal of the American Medical Association points out that in the morning after 24 hours of sleeplessness, a person' s motor performance is comparable to that of someone who is drunk. Curiously, surgeons who believe that operating under the influence of alcohol is grounds for sacking often don' t think twice about operating without enough sleep.

"I could tell you horror stories," says Jaya Agrawal, president of the American Medical Student Association, which runs a website for residents. Some are terrifying." I was operating after being up for over 36 hours," one writes. "I literally fell asleep standing up and nearly planted my face into the wound."

"Practically every surgical resident I know has fallen asleep at the wheel driving home from work," writes another. "I know of three who have hit parked cars. Another hit a 'Jersey gate' on the New Jersey Expressway, going 105kin/h."

"Your own patients have become the enemy," writes a third, because they are "the one thing that stands between you and a few hours of sleep."

The U.S. controls the hours of pilots and truck drivers. But until such a system is in place for doctors, patients are on their own. If you're worded about the people treating you or a loved one, you should feel free to ask how many hours of sleep they have had and if more rested staffers are available.

Sleep is a funny thing because ______.

A．the longer one sleeps, the less sound sleep he gets

B．the more sleep one gets, the more likely a stroke occurs

C．many people stick to about eight hours of sleep to stay fine

D．many people who sleep six hours a night still feel energetic in the day