单项选择题
A large basin cut into the shore，closed off by a caisson，and used for drydocking of ships is known as a（）.
A.slipway B.graving dock C.ground warp D.caisson dock
单项选择题 （） is not usually used in liquid cargo systems.
单项选择题 （） is not one of the winch controls.
单项选择题 When checking the oxygen content of the cargo tanks prior to loading cargoes requiring vapor recovery，the atmosphere must be sampled（）.
