The correct answer is D. The short, medium, and long-term time horizons for the business. In innovation management, a portfolio approach means using a balanced mix of engagement mechanisms rather than relying on a single activity or method. Different mechanisms of engagement generate different types of innovation outcomes, and these outcomes unfold over different time horizons.

Some engagement methods may produce immediate incremental improvements, such as operational ideas or quick problem-solving suggestions. Others may support medium-term opportunities by developing stronger collaboration, cross-functional ideation, or structured concept development. Still others may contribute to long-term strategic innovation by surfacing disruptive ideas, building innovation culture, and strengthening intrapreneurial capability across the organization.

This is why a portfolio approach is valuable. It helps organizations avoid focusing only on short-term gains while neglecting future growth opportunities. Within GInI-related innovation topics, engagement is not only about collecting ideas but also about shaping a sustainable innovation system that supports current performance and future renewal. The impact therefore spans multiple business time horizons, making option D the best and most complete answer.