煤气常用隔断装置有哪些？
参考答案：
煤气常用隔断装置有阀门、水封和盲板。
-There _____ a class meeting this afternoon.
-Yeah，exciting.[ ]
A. are going to be
B. is going to be
C. is going to have
D. will have
活塞在气缸中运动的极端位置称活塞的行程。
