Let's observe the pattern:
2 → 6 (+4)
6 → 12 (+6)
12 → 20 (+8)
20 → 30 (+10)
30 → ? (+12)
So, the next term is:
30 + 12 = 42
Which letter replaces the question mark? A, D, G, J, M, ?
Complete the series: AZ, BY, CX, ?