Analogy — “Nuts : Bolts”. Choose the pair that mirrors a fixed, idiomatic duo used together to denote essentials/complements.

Introduction / Context:
“Nuts and bolts” is both a literal complementary pair (hardware) and an idiom meaning the practical essentials. The best parallel is another entrenched two-word idiom that similarly connotes getting down to core, practical details.

Given Data / Assumptions:

• We prefer idiomatic unity over mere co-occurrence or antonymy.
• The semantic force should be similar—essentials/fundamentals.

Concept / Approach:
“Nitty-gritty” is a classic idiom for core practical details, just as “nuts and bolts” is. This preserves both the fixed-collocation character and the meaning.

Step-by-Step Solution:

Verification / Alternative check:
“Salt : Pepper” is also a common complementary pair, but it lacks the idiomatic “essentials” meaning. The analogy emphasizes both complementarity and idiom.

Why Other Options Are Wrong:
They are either antonyms or non-idiomatic adjective–noun pairs.

Common Pitfalls:
Choosing any familiar pair without ensuring idiomatic semantic alignment with “nuts and bolts.”

Final Answer:
Nitty : Gritty