The correct answer is A. Thyroxine.
Thyroxine is a hormone produced by the thyroid gland. It is essential for normal growth and development, and it helps to regulate metabolism. Thyroxine is made up of four iodine atoms, and it is the only hormone in the body that contains iodine.
Testosterone is a hormone produced by the testes in men and the ovaries in women. It is responsible for the development of secondary sexual characteristics, such as facial hair and muscle mass. Testosterone is also important for sexual function and fertility.
Insulin is a hormone produced by the pancreas. It helps the body to use glucose for energy. Insulin is necessary for people with diabetes, as they do not produce enough insulin on their own.
Adrenaline is a hormone produced by the adrenal glands. It is released in response to stress, and it helps the body to prepare for a fight-or-flight response. Adrenaline increases heart rate, blood pressure, and blood sugar levels.
In conclusion, the only hormone that contains iodine is thyroxine.