吸收塔开人孔前应进行（）操作。
A.空气吹扫
B.停闭路循环水
C.脱盐水冲洗塔盘
D.氧含量分析
参考答案：A, C
The teacher speaks very loudly all the students can hear her.
A．so that
B．because
C．since
D．When
水泥等易飞扬的细颗粒施工材料应密闭存放，砂石等散料应采取覆盖措施
