A Comet Has a Tail Because

A comet has a tail because

A) it elongates as it travels through space, which creates the appearance of a tail.
B) when it comes close enough to the sun, some of its volatile materials start vaporizing and vent into space, creating a tail.
C) when it travels fast enough, it heats as a result of friction and some of its volatile materials start to burn, producing a tail.
D) when it enters Earth's atmosphere, the friction causes it to begin to vaporize, producing a brilliant trail of light.