Final answer:
Option (A), Apple, Samsung, Motorola, and BlackBerry compete in an oligopolistic market structure where a few companies dominate the market.
Step-by-step explanation:
The companies Apple (iPad), Samsung (Galaxy Tab), Motorola (Xoom), and BlackBerry (PlayBook) operate in an oligopolistic market. This type of market is characterized by a small number of firms dominating the market, with high barriers to entry. These firms have considerable market power and make strategic decisions regarding output, pricing, and other competitive moves based on the actions of the other firms in the market. They face the temptation to either collaborate, resembling a monopoly, or to compete with one another to enhance profits by increasing production and reducing prices.
Competition in oligopolies includes elements of both monopoly and perfect competition, and firms often compete on the basis of price, advertising, and product differentiation. The tablet market with firms like Apple, Samsung, Motorola, and BlackBerry is a prime example of an oligopoly as these companies control a significant portion of the market and face little immediate threat from new entrants due to the high costs and technological expertise required to compete.