Answer:
d. neither will advertise.
Explanation:
A game theory is used to analyse the choices of firms in an oligopoly.
A collusion is when two or more firms come together to make a decision usually concerning price.
If both firms advertise, the profit is less than when both firms don't advertise. Therefore, if both firms collude, they would agree not to advertise in order to maximise profits.
But the Nash equilibrium would be for each firm to advertise.
Nash equilibrium is the best strategy for a player in a game regardless of what the other player plays.
I hope my answer helps you.