Final answer:
The business example that exhibits strong rivalry among existing competitors and buyer power is monopolistic competition. Focusing on the options provided, the business example that exhibits strong rivalry among existing competitors and buyer power is monopolistic competition (d).
Step-by-step explanation:
Monopolistic competition refers to a market structure where there are many firms competing to sell similar but differentiated products. In this type of market, there is a high level of competition among firms, leading to limited market power for individual businesses. Buyers in monopolistic competition have the power to choose between different products and can influence pricing and other factors through their choices.
In contrast, a monopoly in a niche market (a) indicates a market with only one dominant firm, while an oligopoly with differentiated products (b) suggests a few large firms competing in a market. Perfect competition (c) is a market structure characterized by many small firms selling homogeneous products, where rivalry among competitors and buyer power are limited.