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问题 问答题

小旭同学做红磷在氧气中燃烧的实验，燃烧一段时间后，小旭同学发现燃烧的红磷己经熄灭，他立刻将燃烧匙取出，但此时红磷又开始燃烧，小旭同学很疑惑．请你用所学的化学知识帮助他解答这一现象，根据这一现象说出消防队员在扑灭火灾后应注意什么？

答案

根据灭火的原理：可知开始红磷熄灭的原因是集气瓶内的氧气的含量低（或被消耗尽），但红磷的温度还高于它的着火点，这时将燃烧匙取出，红磷又接触到氧气，所以又开始燃烧．消防队员扑灭火灾后应注意：清理火灾现场时要不断喷水降温，防止死灰复燃．

单项选择题

(三) Researchers have shown that noise can adversely affect human in both physiological and psychological ways. Hearing losses in particular occupations such as ship - building and con- structi - on work are well - known. In fact, however, we all find hearing more difficult as we age. Young ears can distinguish a wide range of sounds from low to very high frequencies, while older ears lose the ability to distinguish high -pitched sounds. A comparison of people living in some industrialized and non - industrialized areas suggests that this hearing loss may not necessarily accompany old age. Furthermore, a closer inspection of other data reveals economic effects. For instance, an increased turnover in property has been observed in noisy areas near airports. Job performance can be adversely affected by loud noise, especially if accuracy and mental effort are involved. The use of outdoor areas for conversation is not possible for an estimated 5 to 10 million people who live or work in urban areas. When interference with television or speech or sleep is included, as many as 22 to 24 million people can be said to have lost part of the use of their homes and grounds because of noise. Thus noise pollution is a serious environmental concern. The indifferent attitude toward noise should be overcome; considerable efforts should be made to alert people to the grave effects that may stem from an excessively noisy environment.

According to the passage, noise affects human beings______

A．physiologically, psychologically and economically

B．physiologically and psychologically

C．physiologically and economically

D．psychological and economically
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单项选择题

安全电子商务交易的核心机构应为（）

A.网上银行

B.CA机构

C.政府部门

D.EDI中心
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