The correct option is D proline
Option A, lupine, means of or relating to wolves.
Option B cervine means relating to deer; deerlike.
Option C, feline means relating to or affecting cats or other members of the cat family.
Option D, proline means an amino acid which is a constituent of most proteins, especially collagen, which is a part of biochemistry.
Hence from the above options, option D is the different one as the other three relate to animals while proline relates to chemistry.
Hence option D Is the correct answer.