Which of the following is a possible scenario that could lead to a new species?

a) a tree frog needs to jump higher to escape predators. the frog's offspring jump higher due to the frequency of jumping by the parent.
b) over time, many mutations occur in the gene pool of a population of butterflies.
c) a giraffe stretches its neck to reach the leaves at the top of the tree. the offspring are born with necks that are longer than the parents due to the stretching.
d) a bird and a frog reproduce with one another, creating a "brog."