The correct option is C Speciation is a function of time and area
Biodiversity exhibits a latitudinal gradient - it is greatest near the equator, and decreases as you move away from the equator towards the poles. The reason why we see such a pattern has been explained through many hypotheses, one of it being that, speciation is a function of time and area. The tropics covering a vast area, have given rise to a lot more species than the temperates or the Arctic Tundra. Further, the tropics have been relatively unaffected by natural disasters, while the other regions on the planet have been subjected to many glaciations and therefore, the tropics have developed a lot more species over time. Rainforests are in fact, the oldest biome on the planet and therefore, have the greatest biodiversity.