Correct option is B
Series:
G3, I6, ?, M12, O15
Separate letters and numbers.
Letters:
G (7)
I (9)
?
M (13)
O (15)
Pattern: +2 each time
7 → 9 → 11 → 13 → 15
11th letter = K
Numbers:
3 → 6 → ? → 12 → 15
Pattern: +3 each time
3 → 6 → 9 → 12 → 15
So missing term = K9
Final Answer: (B) K9