Gasoline-powered vehicles emit a lot of harmful materials. Nitrogen oxides are formed when atmospheric nitrogen reacts with oxygen at the high temperatures found in a car engine. Carbon monoxide is a by-product of incomplete combustion of hydrocarbons. Evaporated and unused fuel releases volatile hydrocarbons into the atmosphere to help form smog. The presence of a catalytic converter in the exhaust system of the car causes these materials to react and be changed into less harmful products.
Bend village was located 20 miles away from Mound village. People in Bend village used gasoline powered vehicles, while Mound village used only electrical vehicles.

Which village emitted less carbon monoxide?