问题
单项选择题
On a ship，firefighting equipment must be inspected once every（）.
A.three months
B.six months
C.twelve months
D.eighteen months
答案
参考答案：C
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On a ship，firefighting equipment must be inspected once every（）.
A.three months
B.six months
C.twelve months
D.eighteen months
参考答案：C