Which of the following best represents an example of negative feedback?

Negative feedback is a regulatory mechanism in biological systems that helps maintain homeostasis by counteracting a change. In the context of enzyme activity and metabolic pathways, negative feedback typically involves the use of inhibitors to reduce or halt the activity of an enzyme when a product reaches a certain level. This regulation is crucial for preventing overproduction or depletion of essential substances in a cell.

Using inhibitors to block enzyme action is a classic example of negative feedback because when the end product of a pathway accumulates to a sufficient concentration, it can inhibit an enzyme involved in its own production. This prevents excessive accumulation of the product, ensuring that the metabolic pathway operates within a necessary range and responds appropriately to the cell's needs.

Other choices reflect processes that do not exemplify negative feedback. For instance, promoting substrate binding and enhancing enzyme activity would lead to an increase in product formation, which could result in a positive feedback loop if not regulated properly. Therefore, understanding the role of inhibitors in feedback mechanisms highlights how negative feedback is essential for maintaining balance within metabolic processes.