Final answer:
Option B describes the customer for whom an independent tour would be most suitable: a group of four retired executives who want to explore Europe at their own pace.
Step-by-step explanation:
Independent tours are a great way for travelers to explore the world at their own pace and on their own terms. Option B, which pertains to a group of four retired executives, is the most suitable customer group for an independent tour. This option provides the necessary flexibility for the customers to customize their travel experience according to their unique preferences and interests. As a result, they can enjoy exploring Europe without worrying about being confined to a rigid itinerary or schedule.