You are presented with the question "How does a greenhouse protect flowers?" and the following answer choices: 
- keeps them away from the sun
 - keeps them warm
 - keeps them out of soil
 - an external framework
 - it needs them
 - keeps them cold
 - rays or beams
 - by indirect light

Now knowing that agreenhouse is used to protect plants by keeping them warm and flower size varies by plant, choose the best answer.


 

  keeps them warm       