Agoiter may form as a consequence of an inadequate intake of

Iodine

Explanation: Goiter can be defined as the abnormal enlargement of thyroid gland, located at the base of the neck just below the Adam's apple.

Although most of the goiters are painless but it may cause cough that created difficulty in breathing and swallowing.

It is caused due to intake of inadequate amount of iodine in food that we eat. When iodine requirement is not met by the food that we eat, then thyroid will not synthesize adequate amount of thyroid hormone, that may result in the formation of goiter.

So, the correct answer is Iodine.