Answer:
The right options are:
B) Difficult entry
C) Mutual interdependence
D) Market control by a few large firms
Explanation: In an oligopoly, there is a small number of large firms dominating a very significant share of the overall market. In addition, an oligopoly is characterized by high entry barriers and the firms sell identical or differentiated products. Moreover, in an oligopoly, firms are interdependent as each firm control a significant market share; so, one firm's policies affect other firms.
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Step-by-step explanation: