Final answer:
The B) competitive structure is the uncontrollable factor for marketers, encompassing market power, product similarity, and barriers to entry, whereas firm characteristics and strategies are within a firm's control.
Step-by-step explanation:
In a domestic environment, the competitive structure of the industry is considered an uncontrollable factor for a marketer. The competitive structure includes market power, product similarity, and barriers to entry—all aspects that a single firm has limited ability to control. Firm characteristics, channels of distribution, price of the product, and promotional measures are generally considered controllable elements, as the firm can develop strategies to optimize each of these areas. Therefore, the answer to which option is an uncontrollable factor for a marketer in a domestic environment is B. Competitive structure.