The coase theorem states that a) the private sector will fail to produce the efficient amount of a public good because of the free-rider problem. b) under certain conditions, private parties can arrive at the efficient solution without government involvement. c) if there are external costs in production, the government must intervene in the market to assure that the efficient level of output is produced. d) public goods should be produced up to the point where the additional benefit received by society equals the additional cost of producing the good.

B

Explanation:

One of the problems in economics is the allocation of goods in the presence of externalities. When externalities are present allocation of goods in private market won't be efficient because private parties won't internalize them and would arrive to an inefficient outcome. For many years this was an argument in favor of government intervention.

However, Ronald Coase showed that assigning property rights of the externality to one of the private parties (no matter which one) would result in an efficient outcome. This is because  the parties with the property right would then internalize the cost. Then in the bargaining process private parties would reach an efficient outcome without the intervention of the government.