吸收塔排氯时，每层塔板排氯的时间控制在（）h。
A.1
B.2
C.3
D.4
参考答案：A
--Aren’t we living a happy life?
--You should not be content with what you have. _______, you must be better in every aspect of your life.
A．What’s more
B．On the one hand
C．In other words
D．Believe it or not
ISO标准砂中细砂约占多少？
