Advertising by Existing Firms in an Oligopolistic Industry

Advertising by existing firms in an oligopolistic industry

A) only exists where natural entry barriers are weak.
B) can be an effective entry barrier to potential entrants to the industry.
C) will increase the expected market share of new entrants to the industry.
D) maximizes joint profits for firms in the industry.
E) allows easy entry to a new entrant with small sales.