“Propensity” is synonymous with “Tendency.” Choose the option that preserves a similar strong-synonym relationship.

Introduction / Context:
Vocabulary analogies often hinge on synonymy. “Propensity” and “Tendency” both indicate an inclination or predisposition. We must select the option that likewise pairs closely synonymous terms.

Given Data / Assumptions:

• Propensity ≈ Tendency (near-synonyms).
• We seek a pair with comparable semantic proximity.

Concept / Approach:
“Audacity : Impudence” are close in meaning—both relate to boldness bordering on disrespect or shamelessness. Other options are opposites or sequence terms: “Prologue : Epilogue” marks beginning vs end; “Master : Slave” are opposites in social roles; “Conduct : Immortality” is not a synonym pair (and mismatched categories).

Step-by-Step Solution:
1) Establish that the stem is a synonym pair.2) Evaluate options for tight semantic equivalence.3) Select “Audacity : Impudence.”

Verification / Alternative check:
Standard thesaurus entries list impudence among words related to impertinent boldness, overlapping with audacity.

Why Other Options Are Wrong:
They are contrasts or mismatches rather than synonyms.

Common Pitfalls:
Letting connotation differences obscure the strong overlap in meaning.

Final Answer:
Audacity : Impudence