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问题 单项选择题

获得优势菌种必须具备的条件（）①有一种能保存的菌种转移到存活力能达到最大的复活培养基上的方法；②有一个不引起种子染菌的接种场所；③具有定量判断种子质量标准的方法；④具有定量测定菌种一系列生理状态变化的方法；⑤选择能满足种子扩大培养的容器和其他环境条件。

A、①③⑤

B、①②④⑤

C、①②③④⑤

D、①③④⑤

答案

参考答案：C

单项选择题

You have probably seen ads (广告) in newspaper or on television for mail-order companies. Perhaps a catalogue (商品目录) has been sent to you. Why do people buy things they have not seen in person Some people believe that things can be bought more cheaply by mail. Another good thing about buying by mail is that it is easier and more enjoyable to sit at home and work through a catalogue than to shop around the stores. With a catalogue from a large company, you have your own shop window for almost everything you want to buy.
Buying from a catalogue is so easy. It saves the shopper’s time and trouble. Sometimes, it saves the shopper’s money, too. But people often buy more than they can really afford(付得起) or need, because many things look so good to them. They can probably pay a certain part of the full price—a down payment. Then they pay a certain amount of money every month until the goods is paid for in full. But by then they often find what they have bought are of no use at all.

What does the word "They" in "They can probably pay a certain part of the full price ... "refer to
[A] People. [B] Shops. [C] Goods.
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判断题

振动筛轴承温度不得超过70度。
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