Fact 1: Burning fossil fuels increases the carbon in the atmosphere.

Fact 2: This atmospheric carbon might be contributing to the greenhouse effect.

Given the two facts above, answer the question "What is contributing to the greenhouse effect?" with the following options: 
- energy of moving objects
 - mining gold
 - Warm air moving into cold air
 - burning fossil fuels
 - acid rain
 - melting ice caps
 - energy usage
 - single-celled organisms


 

    burning fossil fuels     