Task: Question Generation
Input (English): Background Paragraph: 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. 
Story: Hill town was full of gasoline powered vehicles, while Valley town 50 miles away, banned all gas powered vehicles and allows only electrical vehicles or horse-and-buggies.
Output (English): Which town emitted more harmful materials?