Correct Answer: It is the reaction of organisms to the length of day or night.

Solution : The correct option is it is the reaction of organisms to the length of day or night.

Photoperiodism is the plant's reaction to the length of day and night, impacting processes like blooming, dormancy, and other developmental changes dependent on light, and darkness duration. Photoperiodism exists in many species, both in the animal and plant kingdoms. It is a phenomenon caused by changes in day duration that influence the timing of different biological processes like flowering, fruiting, and dormancy. It is especially critical for plants that reproduce sexually by producing flowers, and seeds.