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分解因式：4﹣9x²=（    ）．

Compared to people with bad attitudes，people who are cheerful and relaxed are less likely to suffer from colds，according to a new study.“It’s possible that being upbeat helps the body fight illnesses，” says Sheldon Cohen，the study’s lead researcher from Carnegie Mellon University (CMU) in Pittsburgh.

In a previous（先前的） study，Cohen and his colleagues put cold­causing viruses into the noses of 334 healthy adults. People who tended to be cheerful and lively were least likely to develop sniffles，coughs，and other cold symptoms. People who showed positive feelings were also less likely to mention symptoms to their doctors，even when medical tests detected those symptoms.

Those findings were interesting，but they didn’t prove that a person’s attitude affects whether he or she gets sick. Instead，it was still possible that a person’s underlying personality is what matters. Evidence suggests，for instance，that certain people are naturally more likely to be outgoing and optimistic，with high self­esteem and a sense of control over life. This would mean that who we are，not how we feel，ultimately decides our chances of catching colds.

To figure out which mattered more (personality or emotions)，the CMU team interviewed 193 healthy adults. The researchers talked to each person over the phone every evening for 2 weeks. At the end of the interviewing period，people got nose drops that contained either cold or flu viruses. Then，each person stayed in an isolated room for 5 or 6 days. The results showed that everyone in the study was equally likely to get infected. Their symptoms，however，differed depending on the types of emotions that they had reported over the previous 2 weeks. Among those who reported good moods and had been infected with the flu virus，for example,28 percent developed coughs and stuffy noses. On the other hand，those symptoms struck 41 percent of people who had been less upbeat.

小题1:

What would be the best title for the passage?

A．Smiles Turn away Colds

B．An Interesting Way to Beat Colds

C．Be Outgoing and Optimistic to Fight Colds

D．What Matters More，Personality or Emotions?小题2:

In the previous study，people who showed positive feelings______.

A．didn’t catch colds as often

B．developed cold symptoms more slowly

C．were less likely to have cold symptoms detected

D．were less likely to feel cold symptoms小题3:

What mainly decides our chances of catching colds according to the new study?

A．Personality.

B．Self­esteem（自尊）.

C．Emotions.

D．Attitudes.小题4:

The underlined word “symptoms” probably means________.

A．something that causes cold

B．something that results in cold

C．signs that something exists，especially something bad

D．changes in your body or mind that show that you are not healthy

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