The most important source of oligopoly is: economies of scale. government-created barriers. technological superiority. all of the above.

economies of scale

Explanation:

Economies of scale are the result of increasing returns to scale, this means that the higher the output, the lower the production costs per unit. This means that large producers will have an advantage over smaller producers which will eventually allow them to make more profits and sell at lower prices. After a while, only large producers that are able to manufacture goods at a low price will exist, e.g. car manufacturers.