Final answer:
An oscillator is not part of a negative feedback system; instead, a sensor mechanism, a control center, and an effector mechanism are its critical components.
Step-by-step explanation:
To answer which of the following is not part of a negative feedback system, we have to consider the components that make up such a system. In a negative feedback system, the key components include a sensor mechanism, a control center, and an effector mechanism. The sensor monitors physiological values and reports to the control center, which then compares the value to the normal range. If necessary, the control center will activate the effector to reverse the situation and return the physiology to the normal range. From the options provided, B) an oscillator is not part of a negative feedback system; the sensor, control center, and effector are all critical components of this system.