Final answer:
In the maturity stage of the industry life cycle, Marketing and Sales is the value-chain activity that becomes most important, as firms strive to maintain market share and differentiate products in a competitive environment.
Step-by-step explanation:
The maturity stage of the industry life cycle is characterized by a heightened focus on competition and maintaining market share, as product differentiation becomes more challenging and growth slows down. During this stage, the value-chain activity that becomes particularly important is Marketing and Sales.
Firms increase their efforts in marketing to differentiate their product, sustain brand loyalty, and compete effectively on non-price aspects. Operations may also become a focus to improve efficiency and protect profit margins. However, Research and Development (R&D) is typically reduced as the product and market are well-defined, and major innovations are often less frequent. Finally, while Distribution remains critical for ensuring product availability, the emphasis may shift toward more cost-effective and efficient distribution strategies rather than expansion.