问题
单项选择题
数字电路中用“1”和“0”电平代表（）。
A.电路中信号电压的大小
B.电路的两种工作状态
C.电路中信号的有无
D.“1”代表输入，“0”代表输出
答案
参考答案：B
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数字电路中用“1”和“0”电平代表（）。
A.电路中信号电压的大小
B.电路的两种工作状态
C.电路中信号的有无
D.“1”代表输入，“0”代表输出
参考答案：B
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| Many years ago, I was fresh out of school and working in Denver. I 1 to my parents' home in Missouri 2 Christmas when my car almost ran out of gas. I stopped at 3 gas station about 50 miles from Oklahoma City. I was planning 4 and visit a friend there. While I was standing in line at the cash register (收款台), I said hello to an older couple (夫妇) 5 were also paying for gas. I drove away, 6 had gone only a few miles when black smoke came from the back of my car. I stopped and wondered 7 I should do. A car stopped behind me. It was the couple I had spoken to at the gas station. They said they 8 me to my friend's. When I got home, I wrote him and his wife a thank-you note for helping 9 . Soon afterward, I received a Christmas present from them. Their note that came with said that helping me had made their holidays 10 . "Thank you" —two powerful words. They're easy to say and mean so much. |
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