问题
单项选择题 A1/A2型题
电泳时蛋白质泳动的速率与下列哪项关系最大（）
A.蛋白质的分子结构
B.蛋白质的构象
C.蛋白质在缓冲液中所带的电荷
D.蛋白质的一级结构
E.蛋白质的二级结构
答案
参考答案：C
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电泳时蛋白质泳动的速率与下列哪项关系最大（）
A.蛋白质的分子结构
B.蛋白质的构象
C.蛋白质在缓冲液中所带的电荷
D.蛋白质的一级结构
E.蛋白质的二级结构
参考答案：C
In the past, man did not have to think about the protection of his environment. There were few people on the earth, and natural resources seemed to be____36____ . Today things are___37_____, the world has become too___38____ . We are using up our natural resources too quickly, and at the same time we are___39____ our environment with dangerous chemicals. If we continue to do this, human life on the earth ___40____survive. Everyone___41_____ today that if too many fish are taken from the sea, there will soon be none left. Yet, with modern fishing__42_____ , more and more fish are caught. We know that if too many trees are cut down, ___43____will disappear and nothing will grow on the land. Yet, we ___44_____to use bigger and more powerful machines to __45____more and more trees. We realize that if rivers are polluted with waste products from factories, we will die.___46_____, in most countries wastes are ___47______put into rivers or into the sea, and there are _48_____laws to stop this. We know, too, that if the___49____ of the world continues to rise at the present rate, in a few years, there will not be enough___50_____. What can we do to solve these problems ? It we eat more vegetables and less___51____, there will be more food available for everyone. Land that is used to grow crops __52_____five times more people than land where animals are kept. Our natural resources will _53_____longer if we learn to recycle them. The world population will not rise so quickly if people use modern methods of birth__54_______ . Finally, if we educate people to think about the problems, we shall have a better and clearer ___55____in the future.
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