我国关于蒸馏酒及配制酒卫生标准中对醛类未作限量规定，原因是A．醛类毒性很低 B．生产

— I can't understand why my mother always keeps me hard at my work. 

— When you ____ children of your own, you will understand. [ ]

A. will have

B. are having

C. have had

D. have to have

百米赛跑中，观众是以 ______的方法比较运动员运动的快慢；而终点裁判员是以 ______的方法比较运动员运动的快慢．

下列中西药联用，可协同增强疗效的是()

A.茵陈与氯霉素

B.甘草与水杨酸类

C.金银花与青霉素

D.石膏与四环素

为什么排水管路要进行固定？

170m3新型石灰竖窑，竖窑利用系数0.8t/m3d。