First, we need to clarify what negative feedback means. Negative feedback is a response that is fed back to the input and that tends to reduce the fluctuation of the output. Negative tries to confer stability to the system. So, you can see that the option B. cannot be because if you add more wood to a fire the fire will increase instead of extinguish. The option A implies a signal (from the high temperature) that starts the air conditioner, so it brings the system out of the equilibrium. The option C. indeed signals that the "full" signal es fed back and the organism will stop eating and so it reaches equilibrium. The answer is the option C. not eating any more when you are full.
