数字电路的输入输出的信号都是（）电量。
A.连续变化
B.断续
C.放大
D.缩小
参考答案：B
Eggs, meat, vegetables and other foods can easily be poisoned by microorganisms such as ______.
A．phenomena
B．dilemma
C．diploma
D．bacteria
一个整数，不是正数就一定是负数．______．
