Final answer:
Collusive agreements are challenging to establish in oligopolies due to limited sellers, lack of communication, and high competition.
Step-by-step explanation:
Collusive agreements are challenging to establish in oligopolies due to multiple factors. One reason is the limited number of sellers in an oligopoly, which makes it difficult for firms to coordinate and reach an agreement. Lack of communication between the firms also poses a challenge, as there may be mistrust or uncertainty about the commitment of other firms to the agreement. Additionally, high competition among the few firms in an oligopoly makes it harder to maintain a collusive agreement, as firms are constantly striving to gain a larger market share and may deviate from the agreed-upon terms.