Researchers know there are many drugs that can alter our bodily processes in such a way【C1

Researchers know there are many drugs that can alter our bodily processes in such a way【C1】______affect our emotional experiences. One such set of drugs is commonly【C2】______as sedatives or tranquilizers. They act to "slow us down"【C3】______and make us less responsive. A doctor may【C4】______a tranquilizer for someone who is very tense or very【C5】______and who cannot sleep or function because of his over-arousal (过于兴奋). Emotional disorders of extreme over-arousal are often【C6】______reduced by such drugs.

【C7】______set of drugs is called stimulants. They "perk us up" emotionally and make us【C8】______responsive. A common mild stimulant is caffeine, a drug【C9】______in most coffees. It is because of its caffeine content【C10】______coffee often gives us a "lift", wakes us【C11】______and helps us be more responsive. Some【C12】______are very potent and may effectively counteract extreme depression.【C13】______a doctor"s care, the use of strong stimulants can be very (80).

Other【C15】______of drugs can also have profound【C16】______on our emotions. These include chemicals found in marijuana, narcotics, and hallucinogenic (引起幻觉的)【C17】______such as LSD. These drugs may produce unpleasant【C18】______pleasant feelings. Also they can be very dangerous. Some are strongly【C19】______, and many can cause various kinds of【C20】______.

【C1】

A．that

B．as to

C．in order to

D．which

请帮忙给出正确答案和分析，谢谢！