You are presented with the quiz "What protects plants from the cold?" 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "agreenhouse is used to protect plants from the cold" and "greenhouses are made with glass , fiberglass , polyethylene, or vinyl coverings". 

So, what's the best answer to the question?


 

   Something made of glass, fiberglass, polyethylene, or vinyl        