无码高清视频|成人自拍视频|欧美成人午夜无码A片秀色直播|草美女视频网站|美女被操网站在线观看

單項(xiàng)選擇題

A butterfly valve consists basically of a disc pivoted across the bore of a ring body having the same radial dimensions as the pipe in which it is fitted.According to the above sentence, which of the following statements is not true?()

A.The diameter of a disc is the same as the outer diameter of the pipe
B.We can infer that the valve is opened or closed by rotating the spindle
C.A butterfly valve comprises a disc and a ring body
D.The profile of the butterfly valve is a ring body

微信掃碼免費(fèi)搜題