Based on the English alphabetical order, three of the following four are alike in a certain way and thus form a group. Which is the one that DOES NOT belong to that group? (Note: The odd one out is not based on the number of consonants/vowels or their position in the letter-cluster.)

Identify the position of each letter in the alphabet and calculate the differences between consecutive letters.

a) FHD:

H - F = +2, F - D = +2. (Pattern: +2, +2)

b) VST:

V - S = +3, T - S = +1

c) ZWX:

Z - W = +3, X - W = +1

d) NKL:

N - K = +3, L - K = +1

FHD is the only group with a consistent pattern, making it the odd one out.

Thus, correct option is (a).