单项选择题
A.Hydraulically operated pusher
B.Spread beam sling
C.Revolving roll clamping device
D.Platform sling
单项选择题 Which of the following is the reason that the metacentric height is a valid measure of only the initial stability?（）.
单项选择题 Which of the following will increase the height of the center of buoyancy for your vessel?（）.
单项选择题 Which of the following will increase the positive stability of your vessel?（）.