单项选择题
All the holds to be loaded with grain must be swept（）commencement of loading.
A.Cleanly/during B.Clear/meanwhile C.Clean/between D.Clean/prior to
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（）.
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.
