You are presented with the question "what releases oxygen during the day but not during the night?" and the following answer choices: 
- h2o
 - tulips
 - Oak
 - humans
 - flowers
 - Trees
 - Conifers
 - gravity

Now knowing that plants release oxygen during the day but not during the night and bulbs planted over the years include tulips and daffodils, choose the best answer.


 

  tulips       