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Disastrous explosions have been caused by accumulations of oil or oil vapour in air lines not drainedAccording to the above sentence, which of the following statements is true?（）
A:Oil vapour in air piping are dangerous
B:Explosion will cause oil vapouring in air lines
C:Oil vapour in air piping should be drained
D:Oil in air piping should not be drained

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出自：海船船员证

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