Suppose a state discovered chemical compounds in their water. The source of these chemicals is the waste discharges of industrial plants in another state. This is an example of a(n):

a. market failure where the market price of the output of these industrial plants does not fully reflect the social cost of producing these goods.
b. external cost imposed by the industrial plants of another state.
c. externality where the marginal social costs of producing these industrial goods differ from the marginal private costs.
d. all of these.

d