Identify class of Language(Asked in comment of gate2014-2-36)

Question

Refer --> check selected answer comments  of https://gateoverflow.in/1995/gate2014-2-36.

Answer 1

Answer is (C) part.

For explanation --> check Arjun ji's comment on  selected answer  of https://gateoverflow.in/1995/gate2014-2-36.

Answer 2

Answer : option (C).

Because here x and y are two different string of given alphabet are concatenate.There is no center to differ x and y .if center is possible then option B answers.