Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the odd letter cluster.

BFF

1   2    3    4   5    6   7     8    9  10  11  12  13

 A   B   C    D   E    F   G    H    I    J    K    L   M

 ↓    ↓    ↓    ↓    ↓     ↓   ↓    ↓     ↓   ↓    ↓    ↓    ↓

 Z   Y    X   W   V    U   T    S    R   Q   P    O   N

26  25  24  23  22  21  20  19  18  17  16  15  14

THE LOGIC;

1) DPG,

D = 4 so,

4x4 = 16 = P(16)

4+3 = 7 = G(7)

2) CIF,

C = 3 so,

3x3 = 9 = I(9)

3+3 = 6 = F(6)

3) BFF,

B = 2 so,

2x2 = 4 = D(4)

2+3 = 5 = E(5) not F(6)

4) EYH,

E = 5 so,

5x5 = 25 = Y(25)

5+3 = 8 = H(8)

Thus, BFF is the odd one.