Fact 1: Biodiversity generally increases from the poles to the equator.

Fact 2: Biodiversity and ecosystems are complex systems.

Given the two facts above, answer the question "What generally increases from the poles to the equator?" with the following options: 
- kinetic energy
 - Energy.
 - warmth
 - voltage
 - sun's heat
 - temperature
 - complexity
 - sunlight


 

       complexity  