Companies Delivering Mixed Concrete Know That It Cannot Be Shipped

Companies delivering mixed concrete know that it cannot be shipped farther than twenty-five miles because the concrete might harden in the truck. Citrus County Concrete Company is the only supplier of mixed concrete to customers within a thirty-mile radius. Citrus County Concrete is an example of a(n) :

A) monopoly.
B) oligopoly.
C) monopolistic competition.
D) pure competition.
E) monopsony.