Final answer:
Melatonin is produced by the pineal gland.
Step-by-step explanation:
The correct answer is C. Melatonin; pineal.
The pineal gland is the organ that produces melatonin. Melatonin is a hormone that helps regulate circadian rhythms, including the sleep-wake cycle. It is responsible for making us feel sleepy at night and more alert during the day.
Testosterone is produced by the testes in males and a small amount is produced by the ovaries in females. Insulin is produced by the pancreas. Epinephrine, also known as adrenaline, is produced by the adrenal glands. So, the correct pairing is Melatonin with the pineal gland.