Fact 1: Cross-pollination increases genetic diversity.

Fact 2: Evolution requires genetic diversity.

Given the two facts above, answer the question "What does evolution require?" with the following options: 
- Time and energy
 - Plant reproduction
 - cross-pollination
 - Reproduction
 - gene flow
 - coded genes
 - circulatory systems
 - animals with backbones


 

   cross-pollination      