An Oligopolist Must Be Very Sensitive to Its Rivals Because

An oligopolist must be very sensitive to its rivals because

A) there are so many that their actions are unpredictable.
B) the government doesn't regulate oligopolists when it comes to colluding on prices and quantities.
C) there are so few that their behavior may well have consequences for the firm.
D) oligopolists try not to use non-price competition since it seems to be unfair to the consumer.
E) they have little else to do.