Which of the options below are the advantages of using a product strategy:

A product structure organizes an organization around specific products or product lines. Each product division typically operates as a semi-autonomous unit with its own resources and functional departments dedicated to that product.

• a. Limits career mobility for personnel outside their product line: This is generally considered a disadvantage. Employees become highly specialized within a product line, which can restrict their opportunities to move to other product areas or functional roles across the broader organization.
• b. Allows greater product viability: This is an advantage. By dedicating resources and management focus to a specific product, the organization can better develop, market, and manage that product, increasing its chances of success and longevity.
• c. Restricts problem-solving to a single product: This is generally considered a disadvantage. While it allows for focused problem-solving for a specific product, it can lead to a "silo effect" where solutions are not easily shared across different product lines, potentially leading to duplicated efforts or a lack of holistic organizational problem-solving.
• d. Suited to Fast changes in a product: This is an advantage. A product structure allows for quicker decision-making and adaptation to market changes or technological advancements related to a specific product because the entire division is focused on it.
• e. Fosters a concern for customer demand: This is an advantage. With a dedicated focus on a particular product, the division is often more responsive and attuned to the specific needs and demands of the customers for that product.

Based on the evaluation, statements b, d, and e are advantages of using a product structure.

The option that includes b, d, and e is B.

The final answer is $\boxed{\text{B. b, d, e}}$