A.rising warm airB.proximity to a low pressure areaC.in……

单项选择题（）during the voyage any case or suspected case of plague，cholera，yellow fever，smallpox，typhus or relapsing fever?

A.Has there been
B.Have there been
C.Has there
D.Have there

单项选择题（）day，pilot flag should be displayed from main mast.

A.From
B.By
C.on
D.With

单项选择题（）any sick person on board now apart from the above-mentioned cases?

A.Have
B.Has
C.Is there
D.Are there

单项选择题（）any person died on board during the voyage otherwise than as a result of accident?

A.Have
B.Has
C.Has there been
D.Are there

单项选择题（）any case or suspected case of quarantinable disease，or any case of eruptive disease or any death be discovered，the local quarantine officer must be notified immediately．

A.If
B.Shall
C.Should
D.Whether