A fire hose with a nozzle attached must be
题型：单项选择题
问题：
A fire hose with a nozzle attached must be connected to each hydrant except when exposed to heavy weather or when the（）.
A.fire hose might be damaged by cargo operations
B.vessel is in port
C.fire-main system is not charged
D.fire pumps are used for purposes other than supplying water to the fire main