Fact 1: Operating an automobile usually requires fossil fuels.

Fact 2: Global warming is caused largely by fossil fuel use.

Given the two facts above, answer the question "What contributes to global warming?" with the following options: 
- using wind farms
 - recycling
 - burning coal
 - Greenhouse gases
 - operating an automobile
 - chlorofluorocarbons
 - Greenhouse gasses
 - nuclear energy


 

     operating an automobile    