题干

一只阴极射线管,左侧不断有电子射出,若在管的正下方,放一通电直导线AB时,发现射线径迹向下偏,则:(    )

A             B

A:导线中的电流由A流向B

B:导线中的电流由B流向A

C:若要使电子束的径迹往上偏,可以通过改变AB中的电流方向来实现

D:电子束的径迹与AB中的电流方向无关

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答案(点此获取答案解析)

B

同类题4

阅读下面短文,掌握其大意,然后从各题所给的A、B、C和D项中,选出最佳选项。

    A group of frogs were jumping through the woods when two of them fell into a big hole. All of the other frogs gathered around the 1  to see what could be done to help their friends.

    When they saw how 2  the hole was, the rest of the group agreed that itwas 3 for the two frogs to get out of the hole. In the beginning, the two frogs 4  with all their strength. Some of the frogs shouted into the hole that is was hopeless, just prepare for the fate(命运), others  5shouted that they two should save their energy and give up. But the two frogs continued jumping as 6as they could, and after several hours of hopeless jump they were quite tired.

    At that moment, one of the frogs gave up. He lay down at the7of the hole, and died as the others looked on his helpless sadness. However, the other frog8to jump with every bit of energy he has, even though he was completely worn out. His friends began a new shouting to him to accept his fate, waiting to die. But the frog jumped harder and harder. Finally he jumped so 9that he got out of the hole.

    The other frogs asked him surprisingly, “Why did you continue jumping when we told you it was impossible?” Reading their lips(嘴唇), the amazed frog explained to them that he was10and when he saw their gestures and shouting, he thought they were cheering him up, so he tried harder and finally succeeded.