在证明DNA是遗传物质的几个著名经典实验中,在实验设计思路中最关键的是() A.要用

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问题:

在证明DNA是遗传物质的几个著名经典实验中,在实验设计思路中最关键的是()

A.要用同位素标记DNA和蛋白质

B.要区分DNA和蛋白质,单独地、直接的观察它们的作用

C.要分离DNA和蛋白质

D.要得到噬菌体和肺炎双球菌

考点:高中生物人类对遗传物质的探索过程人类对遗传物质的探索过程题库
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A rabbit is running into his hole. You may ask, “What happened?”

Well, when a rabbit sees something dangerous, it runs away. Its tail moves up and down as it runs. When other rabbits see this tail moving up and down, they ran, too. They know there is danger. The rabbit has told them something without making a sound. It has given them a signal.

Many other animals use this kind of language. When a bee finds some food, it goes back to his home. It can’t tell the other bees where the food is by speaking to them, but it does dance in the air. This tells the bees where the food is.

But animals say things by making sounds. A dog barks, for examples, when a stranger comes near. A cat purrs(发出呼噜呼噜的声音) when pleased. Some birds make several different sounds, each with its own meaning.

But human beings have something that no animals have---- a large number of words about things, actions, feelings or ideas. We are able to give each other information to tell or inform other people what is in our mind or how we feel. By writing words down we can remind ourselves of the things that have happened, or send messages to people far away. No animals can do this. No animals has the wonderful power of language.

No one knows how man learned to make words. Somehow he learned to make them. As centuries went by, he made more and more new words. This is what we mean by language.

People in different countries made different kinds of words. Today there are about fifteen hundred different languages in the world. A very large English dictionary, for examples, contains four or five hundred thousand words. But we don’t know all these. The words we know are called vocabulary. We should try to make our vocabulary larger. Read as many books as possible. When we met a new word, look it up in the dictionary. A dictionary is the most useful book.

小题1:What’s the meaning of the underlined word?

A.标语

B.信号

C.唱片

D.图像小题2:A dog can tell something__________.

A.by giving signals

B.by making different sounds

C.by purring

D.by barking小题3:It has been proved that no animals are able to_________.

A.give the others information

B.express their actions and feelings with words

C.tell others how they feel

D.make different sounds, each with its own meaning.小题4:Generally speaking, what we mean by “vocabulary” is_______.

A.all the words that we know

B.more and more words we use

C.all the words we need

D.the dictionary which contains thousands of words小题5:What must we do in order to make our vocabulary larger?

A.Make more and more new words

B.look up some new words in a dictionary

C.learn more language

D.Try to read as many books as possible

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在海关监管年限内,减免税申请人将进口减免税货物转让给不享受进口税收优惠政策或者进口同一货物不享受同等减免税优惠待遇的其他单位的,应当事先向减免税申请人主管海关申请办理减免税货物补缴税款和解除监管手续。

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什么是职业介绍补贴?现行青岛职业介绍补贴发放标准是多少?

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工艺基准就是工件加工时的定位基准。

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分馏塔底重沸炉进料中断的现象不包括()

A、塔底循环泵停泵信号报警

B、分馏塔底重沸炉进料流量低低报警

C、分馏塔底重沸炉联锁停炉

D、塔底泵停泵信号报警

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