This is my own question which may come in intermediate step of aldol condensation in acidic medium (but I don't got a molecule whose aldol condensation represent my doubt exactly). Information is provided so that someone with better sources can search the question details in aldol condensation also.
The favourable thing for (c) to be a major product is conjugation of double bonds and highly acidic nature of hydrogen (resulting in elimination of hydrogen at a higher rate) adjacent to carbonyl group (credit $-$ Rover). According to information I have the above reaction is most probably reversible in nature. (b) should be major product as per mechanism I have given. So which will be the major (or only) product. You may take high temperature conditions if temperature is required as we are doing elimination reaction.
If my molecule have some ambiguity than you may explain for another molecule for the same concept.