Analogy — “Action : Reaction”. Choose the pair that mirrors an initiating act and its direct counter-response.

Introduction / Context:
“Action : Reaction” signals an initiating force/act followed by a countering response. In social/behavioral terms, to “assail” (attack) invites a “defend” (protect/repel) response. We must choose the pair that preserves this initiate–counter pattern most cleanly.

Given Data / Assumptions:

• Action → reaction is directional and complementary.
• We seek verb-to-verb pairing expressing opposed roles.

Concept / Approach:
Evaluate each option for a natural counter-response relationship. “Assail : Defend” provides a precise response mapping (attack vs defend). Antonyms alone (introvert/extrovert) do not encode action–response; state–treatment is also mismatched.

Step-by-Step Solution:

Verification / Alternative check:
“Attack : Retaliation” (added distractor) also evokes action–response, but “retaliation” is another action rather than a direct immediate defense. “Assail : Defend” is the crisp, complementary response.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing antonyms or remedy relations with the specific idea of an opposed counter-action.

Final Answer:
Assail : Defend