The correct option is B Thyroid
Thyroxine and triiodothyronine are thyroid hormones which target all tissues and stimulate metabolic rate, growth and development. Thyroxine has four iodine atoms while triiodothyronine has three iodine atoms. The dietary iodine serves as source and thus, the injected radioactive iodine would be incorporated into thyroid gland. This makes option B correct. Parathyroid hormone is a peptide hormone and does not contain any iodine atom which makes option D incorrect. Iodine accumulating tumours are spread to lymph node in second stage of thyroid cancer only. This makes option C incorrect. Option A is incorrect as iodine protects chondrocytes in growth plate cartilage but is not required in as high amount as by thyroid gland. Correct answer is B.