Final answer:
Market penetration is the strategy that involves selling more of existing products and services to existing customers.
Step-by-step explanation:
The strategy that involves selling more of existing products and services to existing customers is Market penetration. This strategy focuses on increasing sales and market share by selling to current customers and encouraging them to buy more of the same products or services.
For example, a fast food restaurant may offer limited-time promotions or discounts to its loyal customers, encouraging them to visit more frequently and purchase more meals.