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

Fact 2: Energy from the sun keeps the earth warm, enables plants to grow.

Given the two facts above, answer the question "Greenhouses are used to what, using the energy from the sun?" with the following options: 
- heat skin
 - evaporation
 - protect plants
 - cool air
 - spread flower seeds
 - important habitats
 - food and shelter
 - reserve water


 

   protect plants      