Staying positive through the cold season could be the best defence（防御物） against getting sick, a new American study suggests.
  In an experiment that exposed healthy volunteers to a cold or flu virus, researchers found that people with a generally sunny character were less likely to fall ill. The findings, published in the journal Psychosomatic Medicine, build on evidence that a "positive emotional style" can help ward off the common cold and other illnesses.
  "People with a positive emotional style may have different reactions to the virus," explained lead study author Dr Sheldon Cohen."And when they do get a cold, they may experience their illness less severely."
  Cohen and his colleagues had found in a previous study that happier people seemed less susceptible （易受影响的）to catching a cold, but some questions remained as to whether the emotional quality itself had the effect.
  For the new study, the researchers had 193 healthy adults complete standard measures of personal qualities, physical health and "emotional styles "．Those who tended to be happy, energetic and easy-going were judged as having a positive emotional style,while those who were often unhappy had a negative style. Afterwards, the researchers gave them something containing either a cold virus or a particular flu virus that causes flu-like symptoms（症状）．Over the next six days the volunteers reported on any aches, pains,sneezes they had. Cohen and his colleagues found that happy people were less likely to develop a cold.
  What's more, when happy folks did develop a cold, their symptoms were less severe than expected.People with negative characters were not at increased risk of developing a cold based on objective measures,though they did tend to get them down about their symptoms.
  "We find that it's really positive emotions that have the big effect"，Cohen said, "not the negative ones."
  So can a bad-tempered person fight a cold by deciding to be happy？



What does the underlined phrase "ward off" in Paragraph 2 mean？ ______

A. Get close to.
B. Keep away from.
C. Get used to.
D. Go on with.

What was the purpose of Cohen's new study？ ______

A. To find effective ways to fight illnesses.
B. To test people's different immune responses to cold viruses.
C. To tell differences between happy people and unhappy people.
D. To examine whether health was related to emotional styles.

How did Cohen reach his conclusion？ ______

A. By comparing the experimental results of different groups.
B. By asking the volunteers to complete a form.
C. By collecting data among people with a cold.
D. By recording flu's symptoms.

What did Cohen's new study show？ ______

A. An emotional style is difficult to change.
B. Happy people are immune to cold viruses.
C. People's attitudes towards illnesses are different.
D. Happiness itself helps protect people from colds.