Based on the English alphabetical order, three of the following four are alike in a certain way and thus form a group. Which one does not belong to the group?

We get the above numerical sequences by arranging the letters according to their positions in the English alphabet.
Options A, C, and D follow the sequence given below:

The numerical value of the first letter increases by 6 to give the second letter.
The numerical value of the second letter decreases by 7 to give the third letter.
The numerical value of the third letter increases by 3 to give the fourth letter.

Option B violates the sequence since 21 - 12 = 9 and 17 - 12 = 5

Thus, option B is the answer to the question.