Fact 1: Agreenhouse is used to protect plants from the cold.

Fact 2: Inside a greenhouse, it is the glass roof that creates the warmth.

Given the two facts above, answer the question "What can protect plants from cold?" with the following options: 
- keratin
 - habitat
 - trees
 - heat
 - glass
 - Light
 - fibers
 - peat


 

     glass    