四、阅读短文，根据短文内容回答问题。(共10 分，每小题 2 分)
　　Psychologists (心理学家) are interested in the reasons whysome people like taking part in risky sports.
　　When they studied people who were learning to jump from aplane with a parachute, they found that the parachutists' bodiesproduced large amounts of two hormones ( 激素) , adrenaline ( 肾上腺素) and noradrenaline (去甲肾上腺素) , just before they made their jump. These hormones help to prepare us for any sudden activity. Adrenaline increases the heart beat and provides more sugar for the muscles (肌肉) , while noradrenaline makes us react (反应) more quickly. However, noradrenaline also supplies energy to a part of the brain which controls feelings of pleasure. A feeling of pleasure caused by this hormone makes certain people want to take part in dangerous sports.
　　Another possible reason is the level of excitement in part of the brain. According to some psychologists, the brain tries to manage a certain level of excitement. They believe that people who have a low level of excitement look for new experiences in order to fire themselves with excitement, but people who usually have a high level of excitement try to avoid risks in order not to become overexcited. If the psychologists are right, people with a low excitement level are the ones who enjoy taking part in dangerous sports and activities.
　　It is thought that people with low levels of excitement have a slower-reacting nervous system than people with higher levels. So it may be possible to find out your level of excitement by testing your nervous system. A quick way of doing this is to put some lemon juice on your tongue (舌头) . If you produce a lot of saliva (唾液) , your nervous system has been affected (影响) by the lemon and so you probably have a high level of excitement; if you produce little saliva, you probably have a low excitement level. If you have a low level, you might enjoy taking part in risky sports. However, this does not mean that you have to the try parachuting!
　　34. Did the parachutists' bodies produce large amounts of adrenaline and noradrenaline before they made their jump? ___________________________________________________________________
　　35. What does adrenaline increase and provide? ___________________________________________________________________
　　36. Why do people with a high level of excitement try to avoid risks?
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　　37. How can people find out their level of excitement? ___________________________________________________________________
　　38. Who may enjoy taking part in risky activities? ___________________________________________________________________