Correct Answer: iodine

Solution : The correct option is iodine .

Iodine deficiency is the cause of goitre. The synthesis of thyroid hormones depends critically on the trace element iodine. The thyroid gland requires iodine to produce hormones such as thyroxine (T4) and triiodothyronine (T3), which are essential for the regulation of metabolism and overall growth and development. When there is insufficient iodine in the diet, the thyroid gland enlarges in an attempt, leading to the condition known as goitre.