“Humans should not try to avoid stress any more than they would shun food, love or exercise.” said Dr. Hans Selye, the first physician to document the effects of stress on the body. While here’s no question that continuous stress is harmful, several studies suggest that challenging situations in which you’re able to rise to the occasion can be good for you.
　　In a 2001 study of 158 hospital nurses, those who faced considerable work demands but coped with（设法处理） the challenge were more likely to say they were in good health than those who felt they couldn’t get the job done.
　　Stress that you can manage may also boost immune(免疫的) function. In a study at the Academic Center for Dentistry in Amsterdam, researchers put volunteers through two stressful experiences. In the first, a timed task that required memorizing a list followed by a short test, subjects believed they had control over the outcome. In the second, they weren’t in control: They had to sit through a gory(血淋淋的) video on surgical procedures. Those who did go on the memory test had an increase in levels of immunoglobulin A, an antibody that's the body’s first line of defense against germs. The video-watchers experienced a downturn in the antibody.
　　Stress prompts the body to produce certain stress hormones（荷尔蒙）. In short bursts these hormones have a positive effect, including improved memory function. “They can help nerve cells handle information and put it into storage,” says Dr. Bruce McEwen of Rockefeller University in New York. But in the long run these hormones can have a harmful effect on the body and brain.
“Sustained stress is not good for you,” says Richard Morimoto, a researcher at Northwestern University in Illinois studying the effects of stress on longevity(长寿), “It’s the occasional burst of stress or brief exposure to stress that could be protective.”
The passage is mainly about ________.

A．the benefits of manageable stress

B．how to avoid stressful situations

C．how to cope with stress effectively

D．the effects of stress hormones on memory

The underlined word “shun” (Line 1, Para.1) most probably means________.

A．cut down on

B．stay away from

C．run out of

D．put up with

We can conclude from the study of the 158 nurses in 2001 that ________.

A．people under stress tend to have a poor memory

B．people who can’t get their job done experience more stress

C．doing challenging work may be good for one’s health

D．stress will weaken the body’s defense against germs

Dr. Bruce McEwen of Rockefeller University believes that ________.

A．a person’s memory is determined by the level of hormones in his body

B．stress hormones have lasting positive effects on the brain

C．short bursts of stress hormones enhance memory function

D．a person’s memory improves with continued experience of stress