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问题 填空题

有下列物质①氢气②液氧③二氧化碳④自来水⑤四氧化三铁⑥矿泉水⑦空气，

请用这些物质前的序号填：

（1）属于混合物的有 ____            _____ ；

（2）属于纯净物的有 __           _______ ．

答案

（1）④⑥⑦

（2）①②③⑤

单项选择题

When college students were asked about their experiences in childhood, those who remembered their parents frequently being in pain were also those who experienced common pains, like headaches, most frequently as adults. This evidence argues that a person’s childhood observations of adults in pain can make that person more susceptible to pain as an adult.
Which of the following, if true, most seriously weakens the argument above

A．Students who most frequently remembered that they were in pain as children were no more likely than the average student to experience common pains very frequently.

B．Parents who were frequently in pain when their children were growing up often experience just as much pain after their children have grown up.

C．College students are in general less susceptible to common pains, like headaches, than are older adults.

D．Adult memories of the circumstances of childhood pain are often vivid, but adults can rarely recall the subjective experience of being in pain as a child.

E．(E) A person’s adult recollections of childhood are likely to emphasize those memories that reflect the person’s adult experiences.
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判断题

《石油工业动火作业安全规程》SY/T5858-2004规定：特殊动火、一级工业动火作业票有效时间不超过8小时。
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