请简述新装置开工前吹扫的目的。
参考答案：
①为了清除施工期间存在与管道和设备内部的杂质；
②防止卡住阀门、机泵，确保管线畅通无阻。
The experiment has_________ the possibility of the existence of any life on that planet, but it does not mean there is no life on other planets.
A．found out
B．pointed out
C．ruled out
D．carried out
A．mgtgθ
B．mgsinθ
C．μmg
D．μmg
mgtgθ
mgsinθ