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.
Crossing over, or recombination, is the exchange of chromosome segments between nonsister chromatids in meiosis. Crossing over creates new combinations of genes in the gametes that are not found in either parent, contributing to genetic diversity.
Hope it helps
D looks like the oldest one because there is barley anything there. if not then I would do b