Answer:
Option D is the answer.
Explanation:
An oligopoly is a market in which there are only a few sellers, with each seller offering a product similar or identical to the others.
So, When an oligopoly is in a Nash equilibrium, then - a firm will choose its best pricing strategy, given the strategies that it observes other firms have taken.
Note :
A Nash equilibrium occurs when no participant ( between different participants) can gain by a uniform change of strategy if the strategies of the others remain unchanged. The system is somewhat stable in this equilibrium state.