Alphabet series – identify the next 4-letter block: BCFG, JKNO, RSVW, ?

Introduction / Context:
Letter-block sequences typically apply fixed step sizes through the alphabet. Once the step pattern inside each 4-letter block is known, predicting the next block is straightforward.

Given Data / Assumptions:

• Blocks: B C F G | J K N O | R S V W | ?
• Alphabet positions use A=1, B=2, …, Z=26, with wrap-around past Z back to A if needed.

Concept / Approach:
Within each block, the steps are consistent: +1, then +3, then +1. We also observe that each new block starts several letters ahead of the previous, keeping the same internal stepping.

Step-by-Step Solution:
Check block 1 (B→C = +1, C→F = +3, F→G = +1).Block 2 (J→K = +1, K→N = +3, N→O = +1).Block 3 (R→S = +1, S→V = +3, V→W = +1).Therefore, block 4 must apply the same +1, +3, +1 stepping starting from the next appropriate letter. After W, continue the pattern to the next block start: take Z as the starting letter (wrap-around). Then Z→A = +1 (wrap), A→D = +3, D→E = +1, producing Z A D E.

Verification / Alternative check:
Among the options, only ZADE matches the internal +1, +3, +1 rule exactly from its first to last letter with proper wrap-around.

Why Other Options Are Wrong:
HIKL / STUX / MNPQ do not realize the +1, +3, +1 increments starting from their first letters consistently (or would repeat earlier blocks rather than follow-on progression with wrap-around).

Common Pitfalls:
Forgetting alphabet wrap-around beyond Z; Z→A is a valid +1 move in cyclic letter series.

Final Answer:
ZADE