Choice "C" is correct. Market competitiveness is often the most significant of the five forces facing a firm. Firms need to be able to anticipate the strategic moves of rival firms. If a firm is in competition with other firms who are able to respond to changes in various components affecting business, the firm faces a strong competitive force of intensity of competition (market competitiveness).
Choice "b" is incorrect. Barriers to entry are "hoops" or other obstacles that a firm must combat when it attempts to enter a new market.
Choice "d" is incorrect. A firm faces heavy competition from substitute products when similar products exist in the marketplace, and consumers are easily able to switch from one product to another.
Choice "a" is incorrect. Bargaining power of the customers relates to the ability of the customer to directly impact the profitability of the firm by increasing the negotiating power of the customer.