Which of the Following Best Describes How Cap-And-Trade Is a Market-Based

Which of the following best describes how cap-and-trade is a market-based solution for dealing with carbon dioxide emissions?

A) The market has reduced carbon dioxide emissions without government intervention because companies have self-regulated to remain competitive.
B) The states have reduced carbon dioxide emissions because the federal government has been unwilling to do so.
C) Companies that pollute have spent significant money lobbying Congress to grant them exemptions from environmental regulations.
D) It allows those who reduce emissions to sell credits to those who do not meet environmental standards.