The carbon footprint of an activity is used to assess environmental pollution. what does it measure?
nitrogen oxide
carbon molecules
greenhouse gases

The carbon footprint of an activity measures the greenhouses realeased into the environment and its contribution to pollution. Th carbon footprint can be used to track the activity of a person, a group, an event or an factory/ Organization in a given time frame. The calculation can never be accurate because that would require a lot of data to be collected and because of the factors that are naturally present in nature and are causing carbon dioxide emissions. The carbon footprint may include emissions from fuel, waste and recycling. 

Resistance than a bicycle? i'm not entirely sure