Spring is here, and Brian and his grandfather would like to go fishing for the weekend in Vermont. Brian could either go to the river in town where anyone can fish without a permit, or he could drive up to a stream located on his family's property in the countryside to fish. Assume that, no matter where people fish, all of the fish that are caught would be kept (that is, there is no "catch and release" policy). The fish in the private stream are considered and whereas the fish in the river are and . In other words, the fish in the private stream are an example of , and the fish in the river are an example of .

Fishing in the river will likely lead to because of which of the following reasons?

a. All fishermen will choose to fish in the stream believing that there are more fish there.
b. Nobody will enjoy fishing because of the lack of private contributions to the maintenance of the drier.
c. All fishermen will choose to fish in the river because of the limited access to the stream.
d. Anyone can fish in the river, and one person's fishing activity decreases the ability of someone else to fish with success.