Two goldfish different parents.One fish has a split tail and the other does not.Why do the goldfish have tails with different shapes?

a.Each goldfish has a different tail shape because offspring from different parents will have different tail shapes.

b.Each goldfish has a different tail shape because they have different versions of the gene for tail shape that connect together to make different tail shapes.

c.The goldfish have different versions of the gene for tail shape.The genes are split inside one goldfish's tail but not inside the other's

The goldfish have different versions of the gene for tail shape,which instuct for different proteins that connect in different ways to make different tail shapes.