消除速度常数的单位是（ ）
A．时间
B．毫克／时间
C．毫升／时间
D．升
E．时间的倒数
参考答案：E
He _____ without saying good-bye to them, for he always has good manners.
A．mustn’t have left
B．may not leave
C．shouldn’t have left
D．can’t have left
我国的《公路沥青路面再生技术规范》建议水泥等活性填料一般不超过（）
A.1%
B.1.5%
C.2%
D.2.5%
He _____ without saying good-bye to them, for he always has good manners.