Complete each of the following sentences:
a. A U.S. ____________ awards inventors the exclusive right to production for 20 years.
b. Patents and licenses are examples of government-imposed _________________________ that prevent entry into an industry.
c. When economies of scale make it possible for a single firm to satisfy market demand at a lower cost per unit than could two or more firms, the single firm is considered a ___________________________.
d. A potential barrier to entry is a firm’s control of a(n) _______________ critical to production in the industry.