单项选择题
（）is 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 电缆与船壳板、防火隔堵及甲板的敷设间距不小于（）
单项选择题 泰国人认为人体的（）是不洁的。
单项选择题 A ship can request completion of a （） when the ship is at a higher security level than the port facility or another ship it is interfacing with.
