Which of these organism would have the best chance of becoming part of the fossil record

A. Horse

B. Fish

C. butterfly

D. ant

B. Fish ...

B. Fish, A fish.

Fossilization requires a very specific set of conditions - the creature in question has to have hard parts to be preserved, then it must die and end up somewhere where it won't be eaten or disturbed, it must be Anoxic so it won't decompose normally, it must be buried (relatively) quickly ... The list goes on.