Final answer:
The key advantage of adding a new product line is that it enriches a company's product portfolio, leading to increased consumer choice, potential cost reductions, and overall growth in profitability and market presence.
Step-by-step explanation:
The main benefit of adding a new product line to a company's offerings is primarily B. It adds valuable depth to a company's product mix. This expansion into new product lines can increase profitability and market reach, catering to the various preferences and needs of consumers. An increase in product variety supports the notion that consumers prefer an economy rich in diversity, as it provides them with more options and often leads to better or less expensive products. Additionally, the introduction of new products can sometimes lead to a reduction in costs due to improvements in technology and production processes. This in turn can result in an increase in supply, and coupled with increased demand stemming from better quality or lower prices, it contributes to the company's growth and potential for increased income.