凸轮式刮板流量计的（）在转子园筒壁上的槽内滑动，能伸出也能缩回
A、滚柱
B、凸轮
C、连杆
D、刮板
参考答案：D
If the bottle of gas________fire, the whole building may _________.[ ]
A. catches ; be burned to the ground
B. will catch ; be burned down
C. is on ; burn down
D. will be on; be burned down
减速器箱体加工过程第一阶段将箱盖与底座（）加工。
A.分开
B.同时
C.精
D.半精
