Each lifeboat must be lowered and maneuvered in the water at least once every().
A.2 months
B.3 months
C.4 months
D.5 months
参考答案:B
Each lifeboat must be lowered and maneuvered in the water at least once every().
A.2 months
B.3 months
C.4 months
D.5 months
参考答案:B