You are presented with the question "what co-evolved with plants?" and the following answer choices: 
- gravity
 - peachleaf willow
 - Chemical energy
 - Organic compounds
 - hummingbirds
 - h2o
 - density
 - animals

Now knowing that some birds are pollinators that co-evolved with plants and hummingbirds are an important groups of bird pollinators, choose the best answer.


 

     hummingbirds    