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问题 单项选择题

B细胞表达的CD分子是

A．CD2

B．CDl6

C．CDl9

D．CD28

E．CD8

答案

参考答案：C

解析：
CD2又称淋巴细胞功能相关抗原—2，表达于胸腺细胞、T细胞和NK细胞。 CD8与MHC-Ⅰ类分子结合，CDl6表达于NK细胞表面。CD28表达于外周血所有CD4+T细胞和50%的CD8+T细胞，是协同刺激信号受体，与B7分子结合。

探究题

如果你是一个唐朝时期准备参加科举考试的秀才，得知唐玄宗今年将诗赋作为科举考试的内容，你会怎么做？能否思考一下唐朝的文学界、教育界将会呈现出怎样的局面？

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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.

Unemployment almost always brings changes that are ______.

A．unpleasant

B．unsuitable

C．untenable

D．unworthy
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