网体填料安装时，一层填料盘相邻网片的波纹倾角应（）；相邻两层填料盘波纹方向互成90°。
A、相反
B、相同
C、互成90°
D、互成45°
参考答案：A
The Town Hall ______ in the 1800’s was the most distinguished building at that time.
A．to be completed
B．having been completed
C．completed
D．being completed
SO2的排放浓度是由二氧化硫连续在线监测仪在烟囱入口处对烟气中SO2浓度检测的数值，仪器直接测量的浓度是以ppm表示。
