Which of the following is an example of negative feedback mechanisms?

Negative feedback mechanisms are critical for maintaining homeostasis in biological systems. They operate by sensing changes in a system and initiating responses that counteract those changes, thus helping to bring the system back to a set point or normal range.

In the case of blood pressure regulation, the body utilizes negative feedback to ensure that blood pressure remains within a healthy range. When blood pressure rises, baroreceptors detect this increase and send signals to the brain, prompting the heart to slow down and blood vessels to dilate, which lowers blood pressure. Conversely, if blood pressure drops, the body responds by increasing heart rate and constricting blood vessels to elevate blood pressure back to normal. This continuous feedback loop exemplifies how a negative feedback mechanism operates, ensuring stability in the cardiovascular system.

On the other hand, the other choices represent different types of biological processes. Platelet aggregation during injury is a positive feedback mechanism that accelerates clot formation, childbirth involves positive feedback through the hormone oxytocin to enhance contractions, and ripening of fruit also operates through a positive feedback mechanism driven by the release of ethylene gas. These processes are aimed at promoting a specific outcome rather than maintaining equilibrium within a set range, thus highlighting the difference between them and negative feedback systems.