When whistle signals are used for launchin
题型：单项选择题
问题：
When whistle signals are used for launching lifeboats，one short blast means（）.
A.use the float-free method only
B.lower all boats
C.raise all boats
D.drill is over，secure all boats
When whistle signals are used for launching lifeboats，one short blast means（）.
A.use the float-free method only
B.lower all boats
C.raise all boats
D.drill is over，secure all boats