When a Positive Externality Exists in the Production of a Good

When a positive externality exists in the production of a good,

A) subsidizing the production of the good could correct for the externality.
B) government could correct for the externality by shifting the good's supply curve to the left.
C) an appropriate policy would result in a decrease in the price of the good.
D) an appropriate policy would result in a decrease in the good's output.
E) taxing the production of the good could correct for the externality.