Which of the following is not a barrier to entry that would allow a monopolist to keep potential competitors out of its market?

a. Significant economies of scale exist,

b. The market price of the product is too high,

c. The firm has a patent on the good or control over some resource required for the production of the good,

d. The firm has government authorization to be a monopoly.

The correct answer is B (the market price of the product is too high). A monopoly has various barriers to entry in the market. For instance, it may have significant economies of scale, allowing them to receive resources with hefty discounts hence selling their products at relatively lower prices, making it hard for firms to join the market. Secondly, a monopoly may have power over the scarce resources, which could have been used by other companies, hence creating a barrier to entry. Lastly, the government may have authorized a particular firm to be a monopoly and licensed the firm to produce specific products barring other companies from joining the market. However, the market price is not a barrier since the production cost of a firm may be affordable for companies in the market.