Classification – Odd one out (synonym vs antonym) Each pair relates two words. Three pairs are antonyms or complementary opposites, whereas one pair is a clear synonym set. Identify the synonym pair as the odd one out.

Introduction / Context:
Verbal classification often sets up a majority class (e.g., antonym pairs) against a single exception (e.g., a synonym pair). The skill being tested is precision: can you name the relation and check it consistently across all options? This prevents being misled by general “relatedness.”

Given Data / Assumptions:

• Stale : Fresh
• Truth : Lie
• Slow : Sluggish
• Teach : Learn

Concept / Approach:
Antonyms express opposition (semantic contrast). Synonyms express similarity. “Teach : Learn” are complementary roles in a process (teacher ↔ learner), which many tests still categorize under oppositional/complementary roles. The single unambiguous synonym set here is “Slow : Sluggish.”

Step-by-Step Solution:
Stale ↔ Fresh → antonyms.Truth ↔ Lie → antonyms.Teach ↔ Learn → complementary/contrastive roles within education (often treated as oppositional in analogy sets).Slow ↔ Sluggish → synonyms (both mean lacking speed/energy) → odd one out.

Verification / Alternative check:
Substitute in sentences: replacing “slow” with “sluggish” preserves meaning, unlike substituting “stale” with “fresh” or “truth” with “lie,” which reverses meaning. “Teach” and “learn” invert roles rather than preserve meaning, aligning with the majority’s contrastive spirit.

Why Other Options Are Wrong:

• Stale : Fresh → clear antonyms.
• Truth : Lie → clear antonyms.
• Teach : Learn → contrastive roles; not synonymous.
• None of these → there is exactly one synonym pair.

Common Pitfalls:
Assuming any non-antonym pair is the outlier. Ensure it is specifically synonymous to fit the intended pattern.

Final Answer:
Slow : Sluggish