Classification (antonyms vs related terms): Three pairs show clear opposites; one pair lists related orientation words that are not opposites. Identify the odd pair.

Introduction / Context:
Verbal classification often mixes true antonyms with words that are merely related. Your goal is to discriminate strict opposites from terms that coexist in similar contexts without forming a binary. This skill ensures precise vocabulary control and semantic reasoning under timed conditions, which is common in competitive exams.

Given Data / Assumptions:

• Pairs: Day : Night, Up : Down, Across : Along, Small : Large.
• Antonyms are defined as mutually exclusive endpoints on a single semantic dimension (for example, up vs down).
• Related terms are words that may appear in similar contexts but do not encode direct opposition (for example, across and along describe different directions of movement along a surface or space).

Concept / Approach:
Test each pair by asking: If one term is true, must the other be false along the same axis? If yes, the pair is likely an antonym pair. If no, the terms may be orthogonal or only contextually connected, and therefore are not opposites.

Step-by-Step Solution:

Verification / Alternative check:
Substitute the terms in sentences describing movement: “Walk across the road” vs “Walk along the road.” Both can be true in different scenarios without negating one another. Hence the pair does not encode opposition.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming prepositions in the same domain must be antonyms. Contextual co occurrence does not imply opposition. Focus on whether the dimension is the same and whether the terms negate each other.

Final Answer:
Across : Along