单项选择题
Backstays are（）.
A.Running rigging leading aft from the masts B.Running rigging leading forward from the masts C.Standing rigging leading aft from the masts D.Standing rigging from the cross trees to the mast head
单项选择题 All the holds to be loaded with grain must be swept（）commencement of loading.
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.
