You are presented with the question "What releases oxygen during the day but not during the night?" and the following answer choices: 
- elephants
 - dogs
 - hydrocarbons
 - blue pine
 - Conifers
 - vegetation
 - humans
 - Fuel cells

Now knowing that plants release oxygen during the day but not during the night and plants include blue pine, hemlock, spruce and oak, choose the best answer.


 

    blue pine     