Answer:
The correct answer is A) serotonin
Explanation:
Serotonin is a neurotransmitter that is responsible for regulating sleep, aggression, appetite, etc. Serotonin plays an important role in mood swings, fear, anxiety. Decrease production in serotonin can cause depression, loss of appetite, low energy, negative thoughts, irritation, etc.
Therefore as jack has lost his appetite and is unable to sleep and experience mood swings therefore this shows that the amount of serotonin hormone in jack has diminished. Therefore the correct answer is A.
