Answer:
The forest with the most diverse population is the one that could have this distribution: 25 W, 25 X, 25 Y and 25 Z.
The one that has a distribution like this with 3 species, would be the one that is more diverse.
But anyway, the solution to our problem, the answer to our question is that the stages of stellar evolution, in the correct order, are: a nebula followed by a protostar followed by a main sequence star followed by a red giant and then finally, a white dwarf.