You are presented with the question "a greenhouse is used to protect plants by doing what?" and the following answer choices: 
- reduced heat
 - colder and wetter
 - storing lawnmowers
 - holding plant pots
 - retaining heat
 - In the winter
 - food and shelter
 - starting fires

Now knowing that agreenhouse is used to protect plants by keeping them warm and retains heat in cold weather, reflects exterior heat in warm weather, choose the best answer.


 

     retaining heat    