Pick the ordered 4-letter string to complete the pattern: ab_x_za_cxy_abcx_z.

Introduction / Context:The sequence interleaves motifs from {a, b, c, x, y, z}: “ab…”, “…za…”, “…cxy…”, “…abcx…”, “…z”. We must place one 4-letter option into the blanks to produce standard sub-runs like “abc”, “cxy”, and “xyz”.

Given Data / Assumptions:

• Skeleton: ab _ x _ za _ cxy _ abcx _ z
• Options: cybzy, cxbzy, cyczy, bybzy.

Concept / Approach:The best candidate should (i) close “ab_” into “abc”, (ii) set up “…za b…”, (iii) complete “cxy_” into “cxyz”, and (iv) let the tail realize “…abcx y… z”.

Step-by-Step Solution:1) Insert “c x b z y”.2) “ab + c” → “abc”; next blank “+ x” produces “…x…”, handing off to “…za b…”.3) The third letter “b” yields “…zab…”, a standard bridge into “cxy…”.4) The fourth letter “z” completes “cxyz”, and the residual “y” aligns with “…abcx y… z”.

Verification / Alternative check:Observe canonical clusters: “abc”, “zab”, “cxyz”, and “…abcx y…z”.

Why Other Options Are Wrong:They cause local inversions (e.g., “cyc…”) or disrupt the “cxy→cxyz” completion.

Common Pitfalls:Not accounting for the long tail “abcx_z”.

Final Answer:cxbzy