What section of the brain instructs the pineal gland to release melatonin as nighttime approaches and daylight decreases?

The correct answer is Suprachiasmatic nucleus

Explanation:

Melatonin is a hormone secreted by the pineal gland which plays a major role in sleep regulation in humans. This hormone is majorly secreted at the night time when the light entry reduces in eyes.

The Suprachiasmatic nucleus of the anterior hypothalamus regulates the release of melatonin by the pineal gland in the night by getting the low light signal from the optic nerves. By controlling the secretion of melatonin Suprachiasmatic nucleus controls the sleep-wake cycle in humans. So the correct answer is the Suprachiasmatic nucleus.