关于焦点特性的描述，错误的是A．管电流较大、管电压较低时，有_爱下问搜题

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问题单项选择题

关于焦点特性的描述，错误的是

A．管电流较大、管电压较低时，有效焦点有变大的倾向
B．相同管电压下，焦点随管电流的增加而变大
C．相同管电流下，焦点随管电压的下降而变大
D．管电流的变化比管电压的变化对焦点影响更明显
E．管电流较大而引起焦点变大的原因，是电子间存在引力

答案

参考答案：E

解析：管电流较大而引起焦点变大的原因，是由于电子束的电子之间斥力增大。

完形填空

The Vietnam (越南) War broke out. The young husband        the army and died in the war. His wife and son began to have a        life after that. Even though their life was very hard and sometimes they didn’t have enough food to eat, the        still decided to raise her son by herself.
Several years later her son immigrated (移民) to America        finally became an engineer. He often sent letters to his mother with much money. However, with many excuses, the son        to come back home to visit his mother.
   his mother died, the son returned. But he didn’t cry. His mother left a box behind. During the funeral (葬礼), the son opened the box and        cried and shouted, “Mom! Mom!”        looked at each other and then looked at the box. It was full of $100 bills and a piece of paper.
It read, “Son, I don’t spend too much money. I miss you a lot. Every time I heard a motorcycle       , I ran out of the door but it wasn’t you. I saved money        you in case (以防) you get sick.”

A．comfortable

D．running off

单项选择题

Swing中要响应动作事件必须实现ActionListener接口，而实现ActionListenrer接口必须实现的方法是 ( )。

A．actionPerfonned()

B．focusGained()

C．actionMoved()

D．focusLost()