Fact 1: If a planet becomes too hot then that planet cannot sustain life.

Fact 2: Global warming linked to human emissions of heat-trapping gases is changing the planet's climate.

Given the two facts above, answer the question "Global warming most threatens the Earth's ability to do what?" with the following options: 
- Sustain life
 - reproduce
 - Melt polar ice caps
 - growth
 - protect them
 - Resist erosion
 - to move people
 - Produce fossil fuels


 

 Sustain life        