To order the activities from the greatest to least impact in reducing fossil fuel consumption, we should consider the relative emissions associated with each mode of transportation.
- Walk to work - This has the greatest impact as it has zero fossil fuel consumption.
- Carpool to work - This significantly reduces the number of cars on the road, thereby lowering fossil fuel consumption per person compared to driving alone.
- Drive an electric car to work - While electric cars reduce fossil fuel use compared to gasoline cars, they still depend on the source of their electricity (e.g., if it's generated using fossil fuels).
- Drive alone to work - This has the least impact as it involves the greatest individual fossil fuel consumption.
Given this reasoning, the correct order from greatest to least impact would be:
Walk to work, carpool to work, drive an electric car to work, drive alone to work.
Since this exact ordering is not in your provided options, the best available choice reflecting the understanding that walking has the most significant impact is:
Walk to work, carpool to work, drive alone to work.