What will come in place of the question mark (?) in the following letter series? IK, JL, KM, LN, ? MCQ with Answer and Explanation

Explanation:
T(20)+3=W(23), W+5=B(28→2), B+7=I(9), I+9=18→R. So R.

Explanation:
First letters: C(3)+2=E(5), E+2=G(7), G+2=I(9), I+2=K(11), K+2=M(13). Second letters: V(22)-2=T(20), T-2=R(18), R-2=P(16), P-2=N(14), N-2=L(12). The missing cluster is ML.[reference:9]

Explanation:
First letters: B, H, N, T, Z (+6 each, wrapping). Second: E, K, Q, W, C (+6 each, wrapping). So ZC.