Answer :
c. Customers advocate my product is characteristic of a well functioning "loyalty loop".
A well-functioning loyalty loop is characterized by customers who not only continue to purchase your product but also advocate for it. This means that customers are satisfied and loyal enough to recommend your product or service to others, which can lead to new customers through word of mouth and increase overall brand loyalty.
In contrast, the other options do not necessarily indicate a loyalty loop. For instance, 'a. Customers become employees' is less relevant, 'b. Suppliers offer discounts for bulk orders' is about supplier relationships, and 'd. Loyalty to an ineffective manager causes progressively worse decision making over time' is unrelated to customer loyalty.