相对压强的起点是指( )。
A．一个标准大气压 B．液面压强C．绝对真空 D．当地大气压
参考答案：B
机动车通过铁路道口时可以超车。
Does your father work in a factory?[ ]
A. Yes, he doesn't.
B. No, he does.
C. Yes, he does.
