The correct option is D Connoisseur
'One who is well- versed in any subject; a critical judge of any art, particularly fine arts' is option D, Connoisseur. Option A, 'Veteran' is a person having long experience in a particular field. Option B, 'Philistine' is a person indifferent to culture and arts. Option C, 'Dilettante' is a person who is interested in a subject but doesn't have a deep understanding of it. Thus, options A, B and C are incorrect and the correct answer is option D, Connoisseur.