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

單項選擇題

An advantage of a helical gear pump over a simple gear pump is that the helical gear pump is capable of ().

A.maintaining a steadier speed
B.delivering liquids over greater distances
C.operating for longer periods of time
D.producing a smoother discharge flow

微信掃碼免費搜題