Long-run adjustments in purely competitive markets primarily take the form of
a. variations in the cost curves of different firms in the market.
b. entry or exit of firms in the market.
c. evolution of the market from a constant-cost to an increasing-cost industry.
d. product differentiation.

The correct answer (b)

Explanation:

Competitive markets are considered an important and efficient market system which helps to use scare resources to provide goods and service. In the competitive market, long-run adjustment is all about firms entering and exiting the market. The firm which takes loss exit the market likewise, new firms enter the market this is how competitive market works. Enter and exit of firms helps to create equilibrium is long-run.

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