Why is the figure considered to be an example of a negative

Why is the figure considered to be an example of a negative feedback system, as opposed to a positive feedback system?

Solution

A negative feedback system is a regulatory mechanism, applicable to physiological as well as physical and chemical systems. In this system, a stimulus or signal brings about an increase or decrease in the output, but when the threshold level of the output is surpassed, the system is brought back to equilibrium. Thus a negative feedback system tends to bring back the feedback cycle back to its original level.

This is opposed to a positive feedback system, where a stimulus or signal increases or decreases the output and it remains as such, not returning to the original level.

Hence option (4) is correct. The figure illustrates the correction of an imbalance back to a baseline. This fact distinguishes a negative feedback system (as illustrated) from a positive feedback system.