Fact 1: Agreenhouse is used to protect plants from the cold. Fact 2: Greenhouses are made with glass , fiberglass , polyethylene, or vinyl coverings. Given the two facts above, what protects plants from the cold?

Possible answers:
1). Something made of fruit or vegetables
2). series of enzyme-mediated reactions
3). Something made of glass, fiberglass, polyethylene, or vinyl
4). Something whose growth is discouraged by heavy wet soils
5). keeping food fresh for long periods of time
6). Something made of brick
7). Something made of metal
8). gas layer that surrounds earth
The answer is:
3).