Final answer:
Monopolistic competition is characterized by many firms selling differentiated products with low barriers to entry, contrasting with oligopoly and monopoly that have fewer firms and higher barriers.
Step-by-step explanation:
The characteristics of monopolistic competition include a market structure where there are many firms that compete by selling differentiated products that are similar but not identical.
This type of competition is marked by a low barrier to entry, meaning new firms can enter the market with relative ease compared to structures like oligopoly or monopoly where entry is significantly more difficult.
In contrast to monopolistic competition, oligopoly involves only a few firms that dominate the market, often with high barriers to entry, while monopoly signifies a market with a single firm and significant barriers, preventing other firms from entering.
Therefore, the correct answer to the student's question is that firms in monopolistic competition sell similar, but not identical, products, with low barriers to entry.