Which of the following conditions must be met for a single seller to become a monopolist?

a. The firm must have something unique to sell,

b. The firm must have a way to prevent potential competitors from entering the market.

The correct answer is b. The firm must have a way to prevent potential competitors from entering the market.

• If the company has no way of preventing new entrants in the market, entrepreneurs will spot the profit-making opportunity and will saturate the market, increasing competition. On the other hand, if the firm can prevent access to the market (e.g. through a patent or legislative power), then it will remain the sole seller in the long-run and thus become a monopolist.