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问题 选择题

为鉴别分别盛有空气、氧气、二氧化碳的三瓶气体，应选用的方法是（   ）

A．将气体分别通入水中

B．将气体分别通入澄清石灰水中

C．将气体分别通入盐水 中

D．将燃着的木条分别伸入三瓶气体中

答案

答案：D

A、二氧化碳会与水生成碳酸，但是也没有现象，氧气和空气都不会与水反应，不能鉴别，故A错误；

B、根据氧气和空气都不会使石灰水变浑浊，不能鉴别，故B错误；

C、空气、氧气都不会与盐水反应，不能鉴别，故C错误；

D、燃着木条在空气中现象不变，在氧气中燃烧更旺，在二氧化碳中熄灭，现象不同，可以鉴别，故D正确．

故选D

填空题

轨道车乘务人员不足（）严禁运行。
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单项选择题

Losing a job or not being able to find one almost always brings unwelcome changes. If you’ve lost a job, the first feeling is often one of shock. On top of the loss of income, many people find the whole routine of their life is shattered, their contact with other people reduced, their ambitions halted and their identity as a worker removed.
There may be good feelings too—it’s nice to be able to lie in bed in the morning, to spend more time with children, or to have more time to think—a better job may be just around the corner. But, unless a better job does turn up, chances are the days start getting longer and the time becomes harder to fill. Many people pass through periods of difficulty in sleeping and eating. They feel irritable and depressed, often isolated and lonely.
Despite all these problems, unemployment can be a chance for a fresh start. You can discover that it provides an opportunity to sort out or rethink what you want from life and how best you can get it. You can use the time to plan how to find a new job, learn a new skill, develop your hobbies, see if you can run your own business, do some voluntary work in your community or meet new people. It’s up to you.

According to the passage, when a person has first lost a job, more often than not, he feels ______.

A．excited

B．isolated

C．shocked

D．depressed
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