Select the one which is different from the other three responses ........

Explanation:

All options follow order 

HGDC  ---->  (H) 8 - 1 = 7(G)
                      (G) 7-3  = 4(D)
                       (D) 4 -1     =3 (C)

means subtract 1 from first letter , 3 from second letter and 1 from third letter.

But option (3) BAZY  does not follow this pattern