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问题 选择题

如图所示，玉米种子中组成胚的是（　　）

A．①②③④

B．②③④⑥

C．③④⑤⑥

D．①④⑤⑥

答案

图中玉米种子由①种皮，②胚芽，③胚轴，④胚根，⑤胚乳，⑥子叶组成，①种皮有保护作用，胚由②胚芽、③胚轴、④胚根、⑥子叶组成，胚乳中含有丰富的营养物质．故选：B

单项选择题

Visitors to this country are normally admitted for six months, but foreign students can usually stay for one year. They must (54) an educational institution, and they are required to study for a (55) of fifteen hours a week on a daytime course. Prospective students have to show that they can afford their studies, and that they have sufficient (56) resources to support themselves (57) in this country.

In order to work here the foreigner needs a work permit, (58) must be applied for by his prospective employer. The problem here is that the Department of Employment has the right to grant or (59) these permits, and there is little that can be done (60) it; it would be extremely unwise for a foreign visitor to work (61) a permit, since anyone doing so is liable to immediate deportation (驱逐出境). There are some people from the European countries, who are often given (62) residence permits of up to five years. Some other people, such as doctors, foreign journalists, authors and others can work without permits, and foreign students are normally allowed to (63) part-time jobs while they are studying here.

63().

A.engage 

B.take 

C.expect 

D.work
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问答题 简答题

焦化厂常用的从焦炉煤气中回收苯族烃的方法是什么？
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