关于X线产生的叙述，错误的是（）。
A.必须有高速电子流由阴极向阳极行进
B.必须向X线管两极提供高电压
C.乳腺X线管的靶面由钨制成
D.由靶面接受高速电子的能量
E.X线管产生的X线仅占总能量的1%左右
参考答案：C
解析：要想产生X线，必须有高千伏产生的电场和真空条件下产生的高速电子流撞击靶面；乳腺摄影用X线管的靶面物质是钼。
A man died and was on his way to another world，either the Heaven or the hell. He saw an extremely magnificent palace half way and the of the palace asked him to stay and in the palace. The man said，“I have been working hard during my life and now I just want to eat and sleep without any .” The owner of the palace said，“If so，there is else better than here for you. There are a wealth of seafood and delicacies. In my palace and you can eat whatever you want without anyone you. Moreover，you can rest I that nothing needs to be done by you.” Then，the man settled down in the palace. At the beginning，the man felt very at the rotation of eating and sleeping. But gradually，he felt a bit lonely and void. So he went to the owner and ，“It is to live by just eating and sleeping every day. Now I show no interest in this kind of life any more. Could you help me find a job？” The owner replied，“Sorry， there is no job here at all.” After another several months，the man could not bear the present life and went to the owner again，“I really could not this sort of life any more. If you do not offer me a job，I would prefer to go to the instead of living here.” The owner of the palace smiled contemptuously， “Do you think it is Heaven here？ It is the hell！”
|