Why is species diversity higher in tropical regions?

• A
  Tropical latitudes have remained relatively undisturbed for millions of years,providing a long evolutionary time for species diversification.
• B
  Tropical environments are less seasonal,relatively more constant and predictable,which promotes niche specialization and leads to greater species diversity.
• C
  There is more solar energy available in the tropics,which contributes to higher productivity. Higher productivity can lead to greater species diversity.
• D
  All of the above.