Final answer:
The relief felt by the class after their instructor decides not to give a pop test can be best explained by the parasympathetic nervous system.
Step-by-step explanation:
The relief felt by the class after their instructor decides not to give a pop test can be best explained by the parasympathetic nervous system. The parasympathetic nervous system is responsible for promoting relaxation and restorative functions in the body. When activated, it slows heart rate, lowers blood pressure, and stimulates digestion. In this situation, the parasympathetic system would have been activated, leading to a sense of relief and relaxation in the students.