Which strategy involves modifying existing products or creating new related products?

The strategy that involves modifying existing products or creating new related products is product development. This approach is centered around enhancing a company's offerings to meet changing consumer needs or to leverage new technologies and trends. By focusing on product development, a business can innovate, capture new market segments, and improve customer satisfaction, ultimately driving growth and competitiveness in the market.

Market development, on the other hand, focuses on expanding into new markets or customer segments with existing products, rather than modifying those products or creating new ones. A turnaround strategy is aimed at revitalizing an underperforming business, which may not specifically involve product modifications. Vertical integration refers to the process of controlling more than one stage of the supply chain, either by acquiring suppliers or distributors, and does not directly address the development of products themselves. Thus, product development is the clear choice for the strategy that specifically pertains to altering or creating products.