单项选择题
（）The main center-line structural member, running fore and aft along the bottom of a ship, sometimes referred to as the backbone.
A.Frame B.Deckbeam C.Stringer D.Keel
单项选择题 （）are to be used for dunnage if you load rice.
单项选择题 （）is known as a long hatch during loading operation.
单项选择题 （）is the tendency of a vessel to return to its origianl position after it is displaced therefrom.
