若LED数码管显示字符“2”的字模式0x5b，则可以判断该系统用的是（）数码管。
A. 共阴极是数码管
B. 共阳极数码管
C. 动态显示原理
D. 静态显示原理
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C51数据类型中关键词“bit”用于定义（ ）。
A. 位变量
B. 字节变量
C. 无符号变量
D. 特殊功能寄存器变量
Listen and respond: Listen to the 5 questions and choose the correct answers.1___________________________
A. Here it is.
B. I'm sorry to say so.
Coffee, please.
D. See you next time.
—————————
A. Very good.
B. Not yet.
C. That's nice.
D. It's far away.
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A. Take your time.
B. Yes, here you are.
C. Never mind.
D. That's too large.
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