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

In the absence of external forces,the center of gravity of a floating vessel is located directly above the().

A.metacenter
B.amidships
C.center of flotation
D.geometric center of the displaced volume

微信掃碼免費搜題