Which is a distress signal? （）

A.A triangular flag above or below a ball

B.The International Code Signal of distress indicated by "JV"

C.A green smoke signal

D.Flames on the vessel as from a burning tar barrel

足够把物质加热到可以发生燃烧的热能是（）。

A、可燃物质

B、助燃物质

C、燃烧

D、火源