Assertion: Melatonin influences the menstrul cycle. Pigmentation and defense capability.
Reason: Melatonin plays an important role in the regulation of diumal rhytm of our body.

Answer

B

Explanation

Melatonin (secreted by pineal gland) concentartion in the blood appears to follow a diumal (day-night) cycle as it rises in the evening and thorugh the night and drops to a low around noon. Because of this light mediated response. The pineal gland may act as a kind of blockgical clock's which may produce circadian rhythms (variations following a 24 hour cycle). In addition, melatonin also influences metabloism. pigmentation, the menstural cycle as well as our defence capability.