What will come in place of the question mark (?) in the following letter series? BDF, HKN, QTW, ? MCQ with Answer and Explanation

Consider three separate sequences: First letters: B, H, Q, Z (+6,+9,+9? Actually B(2)+6=H(8), H+9=Q(17), Q+9=Z(26). Not consistent. Better: Each group has increasing gaps: B to H is +6, H to Q is +9, Q to Z is +9? Let's check second letters: D(4)+6=J(10), J+9=S(19), S+9=B(2 wrapping). Third: F(6)+6=L(12), L+9=U(21), U+9=D(4 wrapping). So pattern +6,+9,+9? Actually +6,+9,+9 is not consistent. Another approach: These are triplets with +6, +9, +9? Let's re-evaluate: BDF to HKN: B+6=H, D+6=J, F+6=L. HKN to QTW: H+9=Q, K+9=T, N+9=W. QTW to ?: Q+9=Z, T+9=C (wrap), W+9=F. So the pattern is +6, then +9, then +9? Actually first step +6, second +9, third +9? Not symmetrical. Maybe it's +6, +9, +11? Let's check positions: B=2,H=8 (+6); H=8,Q=17 (+9); Q=17,Z=26 (+9). So it's +6,+9,+9. Similarly D=4,J=10(+6); J=10,S=19(+9); S=19,B=2(+9 wrap). So pattern is +6, then +9, +9. But maybe it's +6,+9,+9? That seems odd. Could be +6,+9,+11? Not. Given options, ZBE is plausible if we follow +6,+9,+9. So answer A.