You are presented with the question "What have increased over the last decade dramatically" and the following answer choices: 
- gasoline concentrations
 - Warm air moving into cold air
 - Greenhouse gases
 - treehouse gas concentrations
 - movements in the earth's crust
 - concentrated orange juices
 - genetic diversity
 - greenhouse gas concentrations

Now knowing that carbon dioxide concentrations in the air have increased over the last decade dramatically and carbon dioxide is the primary greenhouse gas, choose the best answer.


 

        greenhouse gas concentrations 