Which of the following letter-number clusters will replace the question mark (?) in the given series to make it logically complete?
CO 72, KI 76, SC 82, AW 90, ? ​​

Given: CO 72, KI 76, SC 82, AW 90, ?

Logic: 1st letter + 8, 2nd letter - 6 and numbers are increasing +4, +6, +8 and +10.

For, 1st letter

C + 8 = K, K + 8 = S, S + 8 = A, A + 8 = I

For, 2nd letter

O - 6 = I, I - 6 = C, C - 6 = W, W - 6 = Q

For, number

72 + 4 = 76, 76 + 6 = 82, 82 + 8 = 90, 90 + 10 = 100

So, the missing term is IQ 100.

Thus, correct option is (a).