The correct option is D Metamorphosis, Bones, Nervous system, Iodine
The process of metamorphosis in frogs occurs in the presence of the thyroxine hormone. The thyroid gland secretes thyroxine (TH), a hormone essential for the growth and development of all vertebrates including humans. It helps in the development of bones and nervous system. Iodine consumption in an optimal quantity helps regulate the production of thyroxine hormone.