Final answer:
The largest source of greenhouse gas emissions in the US is electricity production. Therefore, the correct option is D.
Step-by-step explanation:
The largest source of greenhouse gas emissions in the US is d. Electricity production. According to the Environmental Protection Agency (EPA), the use of fossil fuels to produce electricity accounted for 26.9 percent of US emissions in 2020. Fossil fuels can be replaced by renewable sources such as solar, wind, hydro, and geothermal energy.