Answer:
b. False
Explanation:
Firms are not in competition with many other firms in every market structure. Some market structures such as monopolies or oligopolies feature either one single firm, or only a few firms, that frequently collude instead of competing.
Not all firms leave the market as soon as they lose profits. Some do, but others stay. A monopoly can survive decades without increasing its profits.
Not all firms will try to maximize profits, some will try to maximize market share instead, especially in perfectly-competitive market structures.
Not all firms face a horizontal demand curve. In some market structures, demand can be very dynamic, either sloping upwards (increasing) or downwards (decreasing).
