降压孔板的作用？
参考答案：降低双动滑阀前后压降，降低烟气流速，减轻烟气对滑阀的磨损。
18. ---- Are you free after school?
---- Sorry. I’ve planned to treat a friend of mine to dinner _______for his help.
A．in charge
B．in honour
C．in turn
D．in return
不得发布广告的药品是（）
A.处方药
B.中药饮片
C.精神药品
D.化学原料药
