Two characteristics of oligopoly pricing that have frequently been observed are that
a. oligopolistic prices tend to be "sticky" or inflexible, and when the firms do change their prices, they tend to do so together.
b. oligopolistic firms’ prices tend to fluctuate a lot, and these prices tend to move together with each other.
c. oligopolists tend to practice a lot of price discrimination, and there tends to be a wide variance in oligopoly pricing.
d. oligopolistic firms’ prices tend to fluctuate a lot, and there tends to be a wide variance in oligopoly pricing.

oligopolistic prices tend to be "sticky" or inflexible, and when the firms do change their prices, they tend to do so together.

Explanation:

The two characteristics of oligopoly pricing which have been observed are that the oligopolistic prices tend to be inflexible or sticky, and when the firms alter their prices, the firms do so together.

Oligopolistic firms' prices fluctuate a lot; the prices move together with each other. In several oligopolist markets, prices remain inflexible for a long time, even when there are declining costs, they change.

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