97免费在线观看视频,亚洲综合自拍网,黄色毛片免费观看,热久久综合网,免费看日产一区二区三区 狠狠操av,久久久涩涩涩,在线精品免费视频,人人插天天干,久久91精品国产91久久

單項選擇題

It should be apparent that little or nothing is gained by opening a drain at the same time as or after admitting steamThe above sentence probably means ().

A.There is apparent condensate in piping
B.The steam is not discovered after admitting steam
C.The condensate should be fully loaded in the piping as admitting steam
D.The condensate should be fully drained from the piping while admitting steam

微信掃碼免費(fèi)搜題