The 24 hour (diurnal) rhythm of our body such as the sleep-wake cycle is regulated by the hormone:

Options

(a) calcitonin
(b) prolactin
(c) adrenaline
(d) melatonin

Correct Answer:

melatonin

Explanation:

Melatonin is a hormone that regulates the 24 hour rhythm of our body such as the sleep-wake cycle etc. Melatonin is produced by pineal gland in the brain, which is responsible for operation and regulation of the biological clock in mammals.