问题
单项选择题
边长为S的方形野与边长为a×b的矩形野等效的物理意义是()
A．射野面积/周长比相等
B．射野面积相等
C．射野中心轴上原射线、散射线贡献相等
D．射野中心轴上散射线的贡献相等
E．射野中心轴上原射线的贡献相同
答案
参考答案：D
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边长为S的方形野与边长为a×b的矩形野等效的物理意义是()
A．射野面积/周长比相等
B．射野面积相等
C．射野中心轴上原射线、散射线贡献相等
D．射野中心轴上散射线的贡献相等
E．射野中心轴上原射线的贡献相同
参考答案：D
One day my math teacher asked me to help him save back-up copies of his work in the computer. I then realized I was able to 1 the grades for all of his classes. I showed him how to copy files from one disk to another and he 2 me. A few days later he asked me to help him again, because he 3 how to do it. When I began to show this to him, some students in my class 4 and began to talk among themselves 6 . Later that day, at lunch time, I was 5 by several of them. “Hey, could you help us change our grades in math? We’ll 7 you…” I could not believe what I was hearing．I could get paid for something very 8 ．" All right．I'll do it．" The next day my math teacher 9 me to help him out．When he was not paying attention, I began to change their grades from F’s to A’s． I soon became very 10 among my friends. They began to treat me like a god with a magical 11 . I began to change the grades of students．Word 12 quickly and I became very rich． Everything was going fine 13 I was called into the headmaster's office．When I got there, my teacher was mad, and the headmaster had an angry 14 in his eyes． "I have known you for three years now．I don't want to 15 what your teacher said, but I'm afraid that I must．He has too much 16 , " he said．" Do you have anything to say 17 yourself?" he asked． "No．" I said finally．I did not realize how serious my actions had been．I had violated the 18 of my teacher, and the headmaster．And there was no way 19 ．I was forced to leave my school． That was a good 20 for me．
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