Fact 1: Agreenhouse is used to protect plants by keeping them warm.

Fact 2: Plants are Earth's producers.

Given the two facts above, answer the question "What is used to protect producers and keep them warm?" with the following options: 
- an electric stove
 - sweaters
 - green houses
 - dirt
 - animal fur
 - In the winter
 - evaporation
 - plant fans


 

   green houses      