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

Fact 2: If the weather is warm, their temperature rises.

Given the two facts above, answer the question "how is a greenhouse used to protect plants?" with the following options: 
- prevent heat loss
 - raising their temperature
 - storing water
 - reusing materials
 - increase oxygen
 - It helps them survive
 - reflecting light
 - evaporative cooling


 

  raising their temperature       