If a planet becomes too hot then that planet cannot sustain life.
Global warming linked to human emissions of heat-trapping gases is changing the planet's climate.
If global warming continues, earth may no longer be able to sustain life.
Global warming most threatens the Earth's ability to do what?

[a] Sustain life
[b] reproduce
[c] Melt polar ice caps
[d] growth
[e] protect them
[f] Resist erosion
[g] to move people
[h] Produce fossil fuels