Assertion (A): Goitre is more common in people living in mountainous regions.
Reason (R): The food of people in the mountains lacks iodine.
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Both Assertion (A) and Reason (R) are correct, and R is the correct explanation of A.
In an Assertion-Reason question, each statement is checked for truth first, and then R is tested as the cause of what A describes.
Assertion — correct. Goitre (swelling of the thyroid gland in the neck) has long been common in hilly and mountain areas such as the Himalayan belt.
Reason — correct. Mountain soils lose much of their iodine, so the crops and food grown there contain little iodine.
The thyroid gland needs iodine to make its hormone; when iodine is lacking, the gland enlarges. Lack of iodine causes goitre, so R explains A.