Branchial cyst arises due to-

Ans. is 'a' i.e., Failure of obliteration of second branchial cleft Brachial Cyst* A branchial cleft cyst is a congenital epithelial cyst that arises on the lateral part of the neck usually due to failure of obliteration of the second branchial cleft in embryonic development. Less commonly, the cysts can develop from the first, third, or fourth clefts.* The cyst, usually presents as a smooth, slowly enlarging lateral neck mass that may increase in size after an upper respiratory tract infection.* Treatment is generally conservative.