当检测到上游信号传输失效时，设备向下游发出（）。
A.对告信号
B.告警指示信号
C.含大误码的信号
D.不发任何信号
参考答案：B
How many minutes will it take to completely fill a water tank with a capacity of 3,750 cubic feet if the water is being pumped into the tank at the rate of 800 cubic feet per minute and is being drained out of the tank at the rate of 300 cubic feet per minute ？（）
A.3 min. 36see.
B.6 minutes
C.7min. 30sec.
D.8 minutes
E.1，875 minutes
8088汇编语言源程序由( )组成。
A．段
B．过程
C．子程序
D．标号
