Select the term from among the given options that can replace the question mark (?) inthe following series.

ECQ11, HGO-2, KKM-15, NOK-28, ?​​

Given: ECQ11, HGO-2, KKM-15, NOK-28, ?​​

Logic: 1st letter + 3, 2nd letter + 4, 3rd letter - 2 and difference between number is -9, +13, +13 and +13.

For, 1st letter

E + 3 = H, H + 3 = K, K + 3 = N, N + 3 = Q

For, 2nd letter

C + 4 = G, G + 4 = K, K + 4 = O, O + 4 = S

For, 3rd letter

Q - 2 = O, O - 2 = M, M - 2 = K, K - 2 = I

For number—each number (-13)

11 - 13 = -2 

-2  - 13 = -15 

-15 - 13 = -28 

-28 - 13 = (-41)

So, the missing term is QSI-41.

Thus, the correct option is (b).