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问题 单项选择题

关于蛋白质合成错误的叙述是

A．氨基酸以氨基与tRNA共价相连
B．20种氨基酸都有相应的密码
C．氨基酸与tRNA 3’端连接
D．mRNA是多肽链合成的直接模板

答案

参考答案：A

单项选择题

Can you believe it There’s a world paper shortage. There’s a national bottle shortage, and we’re running out of raw materials like timber and tin -- or so the papers say. Well, I’ve just emptied my shopping basket after my weekly shopping trip and it was full of things made from these scarce materials. Half of what I’d bought I threw away at once; all those unnecessary paper bags, plastic bags, fresh wrapping paper and old newspapers they put the food in nowadays.
Modern packaging makes shopping cleaner and more convenient, but at what cost Every time you throw away a paper bag you’re throwing away part of a tree -- and trees don’t grow overnight! At this rate there soon won’t be any trees left, and then what shall we do
Perhaps we’ll learn to do what my mother did. She used to keep a store of paper bags in a kitchen drawer and use them again and again for her shopping. Most goods were sold loose in those days. And the shopkeeper weighed out the amount you wanted. Of course, liquid goods have always been sold in bottles or cans, but why can’t we use these containers more than once If we re-use all our bottles we would save on the raw materials and energy needed to make new ones. At the moment 90% of our rubbish is just dumped. It’s time we started to think seriously about the growing shortage of raw materials in the world today.

What does the author want us to do
[A] He asks for an awareness of the shortage of raw materials.
[B] He wants us to use paper bags again and again.
[C] He wants us to buy liquid goods.
[D] He wants us to re-use all our bottles.
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判断题

在机车运行过程中，可以用旋转调整手轮的方法来调整均衡风缸的压力。
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