Three of the following four options are alike in a certain way and thus form a group. Which is the option that does NOT belong to that group?

Logic:  Third number = (Second)² − First (for three sets).

5² − 2 = 25 − 2 = 23 
C: 3-2-1

2² − 3 = 4 − 3 = 1 
D: 1-7-48

7² − 1 = 49 − 1 = 48 
A: 2-6-38

6² − 2 = 36 − 2 = 34 ≠ 38 ✘

Thus A does not follow the pattern.

Final Answer:
2–6–38

Final Correct Option:
(a)