(a) The requirement is to describe the reason for the
kinked demand curve in an oligopolist market. An oligopolist
faces a kinked demand curve because competitors will often
match price decreases but are hesitant to match price increases.
Therefore, answer (a) is correct. Answer (b) is incorrect because
an oligopolist does not face a nonlinear demand for its product.
Answer (c) is incorrect because an oligopolist cannot sell its
product for any price. Answer (d) is incorrect because consumer
demand determines the demand curve in all markets.