Answer:
The correct answer is option B.
Explanation:
A monopolistic firm is characterized by a large number of buyers and sellers in the market producing differentiated products which are close substitutes, there are relatively easier entry and exit in the market.
In the given question, Teen Angle Hardware is looking for a niche or a slightly differentiated product to sell to teenagers. But is able to earn only a normal profit because there is a large number of firms in the market. And new firms can enter the market in the long run. So, this firm is an example of a monopolistic firm.