The Productivity Hypothesis Says That There Is Higher Species Diversity

The productivity hypothesis says that there is higher species diversity at the equator than toward the poles because the climate is perfect to grow plants. Besides just the volume of food, why might this allow for there to be more species?

A) There are more places to hide.
B) There is more variety of plants, so there can be species specializing in eating just one type, allowing more species to "fit" in the habitat.
C) Species can be more generalists than specialists, and generalists tend to not go extinct as easily.
D) There are just more plant species toward the equator and that alone accounts for the higher species richness.
E) Rainforests are among the most productive of ecosystems and they tend to be equatorial.