---Only at night ______ to look for food in the desert.

单选题

If headaches only occur at night,lack of fresh air is often the cause.

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单选题

When are you allowed to throw plastic garbage overboard?A. Being more than 25 miles from shore B. Only at night vdien it‘s daikC. Being more than 6 miles from shore D. Never

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单选题

_____ out alone when it is late at night.(　　)

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单选题

I am sorry. But I simply cannot stay up night after night at parties _ work the next morning.

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单选题

Fog signals, required under the Rules for vessels underway, shall be sounded ___ .A. only on the approach of another vesselB. only when vessels are in sight of each otherC. at intervals of not more than one minuteD. at intervals of not more than two minutes

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