Odd-one-out (letter sequences): “Which one differs from the remaining three?” — GIJK, DFGH, CEFG, ABCD.

Introduction / Context:
Letter-sequence items often test recognition of consecutiveness and gaps. Three of these sequences skip a letter between the first two, while one is fully consecutive.

Given Data / Assumptions:

• GIJK: G, (skip H), I, J, K → skip pattern exists.
• DFGH: D, (skip E), F, G, H → skip exists.
• CEFG: C, (skip D), E, F, G → skip exists.
• ABCD: fully consecutive (no skip).

Concept / Approach:
Identify the outlier by the absence of an initial gap.

Final Answer:
ABCD