You are presented with the question "A greenhouse is used to protect angiosperms how?" and the following answer choices: 
- their hosts
 - by keeping them underground
 - by keeping them warm
 - by keeping them outside
 - by keeping them exposed
 - Exfoliation
 - organisms and their habitat
 - In the winter

Now knowing that agreenhouse is used to protect plants by keeping them warm and angiosperms are the flowering plants, choose the best answer.


 

   by keeping them warm      