The pattern followed here is: The first and third letters are increased by + 2.And the second and fourth letters are decreased by - 2.A+2↓C​C−2↓A​I+2↓K​D−2↓B​ Similarly, A+2↓C​W−2↓U​A+2↓C​Y−2W​ Hence, "CUCW" is the correct answer.