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问题 选择题

电磁波和机械波的相同之处是（　　）

A．都可以在真空中传播

B．都可以发生干涉和衍射现象

C．它们在同一介质中传播速度相同

D．都有纵波和横波

答案

A、机械波不能在真空中传播．故A错误．

B、机械波和电磁波都能发生干涉和衍射现象．故B正确．

C、电磁波在真空中传播的速度等于光速，机械波（比如声波）在空气中的传播速度等于340m/s．故C错误．

D、电磁波是横波，机械波有横波也有纵波．故D错误．

故选B．

填空题

在窗体中添加一个名称为Commandl的命令按钮，然后编写如下程序：
Pfivme Sub f(ByVal x As Integer)
x＝x+4
End Sub
Pfivate Sub Commandl_Click()
i＝3
Call f(i)
Ifi>4 Then i＝i*2
MsgBOx i
End Sub
窗体打开运行后，单击命令按钮，则消息框的输出结果为______。
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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 of these examples also point up the fact that attitudes stem from experience. In the one case the experience was direct and impressive, in the other case it was indirect and cumulative. The Nazis were formed largely by the speeches they heard and the books they read.
The classroom teachers in the elementary school are in a strategic position to influence attitudes. This is true partly because children acquire attitudes from those adults whose opinion they respect.
Another reason 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 towards Mexicans.
The media through which the teacher can develop wholesome attitudes are innumerable. Social attitudes (with special reference to races and nationalities) science matters of health and safety, the very atmosphere of the classroom--these are a few of the fertile fields for the induction 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 cheating or scolding them. She can achieve the proper effect by helping them obtain constructive experiences. Finally, a teacher must constantly evaluate her own attitudes, because her influence can be harmful 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 advises teachers to ______.

A. correct the pupil’s incorrect attitude whenever they have
B. ignore the pupil’s incorrect attitude altogether
C. give the proper criticism to the pupil’s incorrect attitude
D. try to use positive experience to develop proper attitude in the pupils
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