Please answer the following question: 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
A:
burning fossil fuels