Explains why it is has improved the problem it was meant to correct

From the list below, please choose a particular environmental policy that is being used in the United States. Write a 4–5-page paper (including the title page and reference list), that accomplishes all of the following:

1. Explains the policy
2. Gives an example where it has been used
3. Explains why it is has improved the problem it was meant to correct
4. Explains how economic principles are used in the design of the policy

Policies

• Carbon tax
• Cap and trade
• Emissions taxes
• Environmental standards (command and control)
• Subsidies for firms that invest in clean technologies