The element of the business model that addresses the question of why a customer should buy from the firm is the value proposition (D).
The value proposition refers to the unique combination of benefits that a company offers to its customers. It answers the question of why customers should choose to buy from a particular firm instead of its competitors.
A value proposition highlights the value, benefits, and advantages that customers will receive by purchasing a product or service from the firm. It communicates the unique selling points and differentiators of the company's offering, making it attractive to customers.
For example, if a company offers high-quality products at a competitive price, that can be part of its value proposition. Other elements of a value proposition could include superior customer service, innovative features, convenience, or a strong brand reputation.
In summary, the value proposition is the element of the business model that addresses why a customer should choose to buy from a particular firm. It communicates the unique benefits and value that the company offers compared to its competitors.