Correct option is C
Given:
D4C3B2A1 , H8G7F6E5 , L12K11J10I9 , ?
Position of Alphabets:

Logic that follows is given as:
D +4 H +4 L +4 = P
4 +4 8 +4 12 +4 = 16
C +4 G +4 K +4 = O
3 +4 7 +4 11 +4 = 15
B +4 F +4 J +4 = N
2 +4 6 +4 10 +4 = 14
A +4 E +4 I +4 = M
1 +4 5 +4 9 +4 = 13
Hence, option (c) is the correct answer.