MCS-51的并行I/O口读-改-写操作，是针对该口的（）。
A.引脚
B.片选信号
C.地址线
D.内部锁存器
参考答案：D
We tried to find a seat on the bus, but they were all_________.
A．used up
B．kept away
C．taken up
D．given away
电能消耗的速率叫做什么？
