As of 2009, what was the greatest source of greenhouse gas emissions?
1. producing electricity
2. transportation
3. industry
4. homes

The greatest source of greenhouse gas emissions is the burning of fossil fuels and the industry that produces the most greenhouse gas emissions as a resut is option 1) producing electricity.

Explanation:

The latest reports for the Environmental Protection Agency (EPA) of the United States say that on a global level it is electricity and heat production that is responsible for up to twenty-five percent of the global greenhouse gas emissions. This includes manufacturing processes that require the burning of coal, natural gas, or oil in order to generate electricity and heat. The second greatest source for greenhouse gas emissions at the global level is agriculture at 24% according to the 2010 figures. This would include the methane gas that is produced from the waste products of large livestock agribusinesses like the beef industry. However, it is more complex to measure the effects of the agricultural sector because ecosystems also remove carbon dioxide from the atmosphere by absorbing carbon in dead organic matter, for example, or and soils.