Markets can have inefficient results if A

• The correct answer is D. All of the above.

The situation in which markets have inefficient results is known as market failure. Market failure happens when the allocation of resources is not efficient. There are different types of market failures such as monopoly power, positive and negative externalities, and non-excludability. Monopoly power is associated with only one firm that has full control over the supply of a good or service leading to an increase in prices and a decrease in supply. Negative externalities are those bad effects that one market transaction has on uninvolved parties. Non-excludability is a common characteristic of public goods in which people who do not pay can enjoy and utilized a good. All of these situations are inefficiencies in the market. Therefore, the correct answer is option D.