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问题 选择题

无性繁殖在生产实践中的益处有

① 繁殖速度快  ② 后代性状均匀一致  ③ 短期内可以获得大量性状一致的植株 ④ 引起品种的退化      [ ]

A. ①③            

B. ①②③            

C. ①②③④        

D. ①④

答案

答案：A

选择题

太阳活动产生的短波辐射和粒子流干扰地球电离层产生了磁暴现象，影响了无线电短波通信。
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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 implies that ______.

A．the teacher should guide all discussions by revealing her own attitude

B．in some aspects of social studies a greater variety of methods can be used in the upper grades than in the lower grades

C．people usually act on the basis of reasoning rather than emotion

D．children’s attitudes often come from those of other children
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