Which is a visible sign of severe iodine deficiency?

The correct answer is Option (2) - Swelling in the neck

A visible sign of severe iodine deficiency is Swelling in the neck.

This condition is known as a goiter, and it occurs when the thyroid gland enlarges in an attempt to compensate for insufficient iodine levels. Iodine is crucial for the synthesis of thyroid hormones, and a deficiency can lead to impaired thyroid function and the development of a goiter. Swelling in the neck is a visible manifestation of this thyroid enlargement.