问题
单项选择题
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
答案
参考答案：B
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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