问题
单项选择题
黑度D定义为（）与（）之比的常用对数值。
A.照射光强L0，透射光强L
B.透射光强L，照射光强L0
C.照射光强L0，反射光强Lf
D.反射光强Lf，照射光强L0
答案
参考答案：A
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黑度D定义为（）与（）之比的常用对数值。
A.照射光强L0，透射光强L
B.透射光强L，照射光强L0
C.照射光强L0，反射光强Lf
D.反射光强Lf，照射光强L0
参考答案：A
(2013·鲁西南名校联考卷)Recently divorced and unemployed，I was on my way downtown to do the rounds of the employment offices.I had no umbrella，for my old one had ____，and I could not ____ another one. I sat down in the ____ and there against my seat was a(n) ____ silk umbrella with a silver handle.I had ____ seen anything so lovely.I examined the handle and saw a carved ___.The usual procedure would have been to ____ the umbrella to the conductor，but an idea __ to me.I decided to take it with me and find the owner myself. I got off the bus in a downpour and ____ opened the umbrella to protect myself.Then I ____ a telephone book for the name on the umbrella.I called and a lady ____. Yes，she said ____，that was her umbrella，which her parents，now dead，had given her as a birthday present.But，she ____，it had been stolen ____ her doorstep a month before. She was so excited that I ____ I was looking for a job and went directly to her house.She took the umbrella，and her eyes were filled with ____.She wanted to give me a ____，but－though twenty dollars was all I had in the world－her happiness at regaining this ____ possession was beyond words and I believed accepting her money would have ____ something.We talked for a while and I left. A week later，I got a job as a sales manager ____.It might be my kindness that paid off.But who knows?
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