D. Pine trees because of the reason being the drop pines
The group of organisms can produce fertile offspring. That is what
makes the group of organisms a species.
I believe it's Sympatric Speciation.
Hope I helped! ( Smiles )
If a population is consider Hardy Weingberg Equilibrium this means that a population will just stay constant from generation to generation, however keep in min there will be things that play a factor in this as well.
I hope this helps answer your question.