Suppose the government auctions off permits to car and truck owners, with each permit allowing the user to emit five tons of carbon dioxide each year from his or her vehicle. The total amount of carbon dioxide permitted is less than the amount currently emitted by vehicles. These permits could then be bought and sold on a market. Which of the following is the best term for this type of system?

Multiple Choice

A command-and-control system

A mitigation allowance

A cap-and-trade system

A price-based adaptation system