The Most Plausible Hypothesis to Explain Why Species Richness Is

The most plausible hypothesis to explain why species richness is higher in tropical than in temperate regions is that

A) tropical communities cover more surface area than temperate communities.
B) adaptive radiation occurred in tropical areas earlier than in temperate areas.
C) tropical regions have species with high birth rates and rapid growth.
D) tropical regions often have more available water and higher levels of sunlight.