Which of the following letter-number clusters will replace the question mark (?) in the given series to make it logically complete?
AAA 5, BCD 10, CEG 15, DGJ 20, ?​

Given: AAA 5, BCD 10, CEG 15, DGJ 20, ?

Logic: 1st letter + 1, 2nd letter + 2, 3rd letter + 3 and number is increasing + 5 place.

For, 1st letter

A + 1 = B, B + 1 = C, C + 1 = D, D + 1 = E

For, 2nd letter

A + 2 = C, C + 2 = E, E + 2 = G, G + 2 = I

For, 3rd letter

A + 3 = D, D + 3 = G, G + 3 = J, J + 3 = M

For, number

5 + 5 = 10, 10 + 5 = 15, 15 + 5 = 20, 20 + 5 = 25

So, the missing term is EIM 25.

Thus, correct option is (a).