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问题 选择题

下列例子中，能够证明遗传多样性的是（　　）

A．人身上有许多细胞

B．蚕豆种子生长成蚕豆

C．同窝小猪的体色有白有花有黑

D．生物圈中的生态系统多种多样

答案

生物多样性通常有三个主要的内涵，即生物种类的多样性、基因（遗传）的多样性和生态系统的多样性．

广义的遗传多样性是指地球上所有生物所携带的遗传信息的总和．但一般所指的遗传多样性是指种内的遗传多样性，即种内个体之间或一个群体内不同个体的遗传变异总和．种内的多样性是物种以上各水平多样性的最重要来源．遗传多样性是生物多样性的重要组成部分．一方面，任何一个物种都具有其独特的基因库和遗传组织形式，物种的多样性也就显示了基因遗传的多样性．另一方面，物种是构成生物群落进而组成生态系统的基本单元．生态系统的多样性离不开物种的多样性，也就离不开不同物种所具有的遗传多样性，因此遗传多样性是生物种类的多样性和生态系统多样性的基础．因此同窝小猪的体色有白有花有黑，证明了遗传多样性．

故选：C．

单项选择题

Of all the areas of learning the most important is the development of attitudes. Emotional reactions as well as logical thought processes affect the behavior of most people.
"The burnt child fears the fire" is one instance; another is the rise of despots like Hitler. Both examples also point up the fact that attitudes stem from experience. In one case the experience was direct and impressive; in the other it was indirect and cumulative. The Nazis were indoctrinated largely by the speeches they heard and the books they read.
The classroom teacher in the elementary school is in a strategic position to influence attitudes. This is true partly because children acquire attitudes from those adults whose word they respect.
Another reason it is true is that pupils often delve somewhat deeply into a subject in school that has only been touched upon at home or has possibly never occurred to them before. To a child who had previously acquired little knowledge of Mexico, his teacher’s method of handling such a unit would greatly affect his attitude toward Mexicans.
The media through which the teacher can develop wholesome attitudes are innumerable. Social studies (with special reference to races, creeds and nationalities), science matters of health and safety, the very atmosphere of the classroom... these are a few of the fertile fields for the inculcation of proper emotional reactions.
However, when children come to school with undesirable attitudes, it is unwise for the teacher to attempt to change their feelings by cajoling or scolding them. She can achieve the proper effect by helping them obtain constructive experiences.
To illustrate, first grade pupils afraid of policemen will probably alter their attitudes after a classroom chat with the neighborhood officer in which he explains how he protects them. In the same way, a class of older children can develop attitudes through discussion, research, outside reading and all-day trips.
Finally, a teacher must constantly evaluate her own attitudes, because her influence can be deleterious if she has personal prejudices. This is especially true in respect to controversial issues and questions on which children should be encouraged to reach their own decisions as a result of objective analysis of all the facts.

The author of this passage tries to ______.

A．present certain facts of how the development of a person’s attitude can be influenced

B．show that our society is not doing enough to help children shape their attitudes

C．point out that teachers are the only people who can influence the children’s attitudes

D．prove that speeches and books are the only factors to indoctrinate children
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单项选择题

下列哪种试验方法不属于三轴剪切试验方法。（）

A.十字板剪切

B.不固结不排水剪切

C.固结不排水剪切

D.固结排水剪切
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