Answer: (3) Ethylene

Explanation-

Ethylene is a plant hormone that plays a significant role in promoting elongation of internodes and petioles in deep water rice (also known as flood-tolerant rice or floating rice). When the rice plants are submerged in water, they sense the reduced oxygen levels, which triggers the production of ethylene. Ethylene induces elongation growth in the internodes and petioles, allowing the rice plant to reach the water surface to access oxygen for survival. This adaptation helps deep water rice to cope with flooding conditions and maintain its growth and development even in flooded environments