Fact 1: Agreenhouse is used to protect plants by keeping them warm.

Fact 2: Flower size varies by plant.

Given the two facts above, answer the question "How does a greenhouse protect flowers?" with the following options: 
- 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


 

  keeps them warm       