Select the letter that can replace the question mark (?) in the following series.

A, D, B, F, D, I, G, ?, K.

M

A, D, B, F, D, I, G, ?, K.

The difference between the first alternate terms is  terms +3, +4, +5, +6 and the difference between the second alternate terms is -2 , such that:

The logic followed here is :

A → (+3) → D → (-2) → B → (+4) → F → (-2) → D  → (+5) → I → (-2) → G → (+6 ) → M → (-2) → K

Thus, the missing term is M