Answer:
The correct answer is parasympathetic nervous system.
Step-by-step explanation:
The conservation of energy is done by the parasympathetic nervous system as it slows down the rate of the heart, enhances the glandular and intestinal activity, and relaxes the gastrointestinal tract's sphincter muscles. It is also termed as the rest and digest system. The system usually becomes more active at the time of sleep and is also the explanation for getting tired after eating or for post-prandial fatigue.