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当前学科：安全生产技术基础
题目：
单选题
把电气设备正常情况下不带电的金属部分与电网的保护零线进行连接，称作（ ）。
A
保护接地（IT系统）
B
保护接零（TN系统）
C
工作接地
D
工作接零（TT系统）
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The easy way out isn’t always easiest. I learned that lesson when I decided to treat Doug, my husband of one month, to a special meal. I glanced through my cook book and chose a menu which included homemade bread. Knowing the bread would take time. I started on it as soon as Doug left for work. As I was not experienced in cooking, I thought if a dozen was good, two dozen would be better, so I doubled everything. As Doug loved oranges, I also opened a can of orange and poured it all into the bowl. Soon there was a sticky dough covered with ugly yellowish marks. Realizing I had been defeated, I put the dough in the rubbish bin outside so I wouldn’t have to face Doug laughing at my work. I went on preparing the rest of the meal, and, when Doug got home, we sat down to Cornish chicken with rice. He tried to enjoy the meal but seemed disturbed. Twice he got up and went outside, saying he thought he heard a noise. The third time he left, I went to the windows to see what he was doing. Looking out, I saw Doug standing about three feet from the rubbish bin, holding the lid up with a stick and looking into the container. When I came out of the house, he dropped the stick and explained that there was something alive in out rubbish bin. Picking up the stick again, he held the lid up enough for me to see. I felt cold. But I stepped closer and looked harder. Without doubt it was my work. The hot sun had caused the dough to double in size and the fermenting yeast made the surface shake and sigh as though it were breathing. I had to admit what the living thing was and why it was there. I don't know who was more embarrassed by the whole thing—Doug or me. When Doug went out the third time, the woman looked out of the window because she was（）
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