重力浓缩工艺水力停留时间一般控制在（）范围内。
A.12-20小时
B.12-30小时
C.20-30小时
D.20-25小时
参考答案：B
There is too much rain these days, isn’t there ? —Yes, it ___ for a week.
A．has been raining
B．had been raining
C．was raining
D．rained
护理诊断：
