From which one of the following,the melatonin is derived?

Daily rhythms are usually associated with

$I.$ Sleep-wake cycle, $II.$ Body temperature, $III.$ Pigmentation, $IV.$ Metabolism, $V.$ Defense capability. All of the above-written activities are influenced/regulated by:

Melatonin is secreted by ..........

The function of the pineal body is to

$I.$ Sleep-wake cycle,$II.$ Body temperature,$III.$ Pigmentation,$IV.$ Metabolism,$V.$ Defence capability. All of the above-mentioned activities are influenced/regulated by: