Assertion–Reason (Two Reasons):\nAssertion (A): Humans are gregarious (social) animals.\nReason (R1): Humans are selfish.\nReason (R2): Humans are gifted with the power of logic and thinking.

Introduction / Context:
The assertion states a broad anthropological observation: humans tend to live in groups and build cooperative institutions. We examine whether each reason causally explains that sociality.

Given Data / Assumptions:

• (A) Humans are gregarious/social.
• (R1) Humans are selfish.
• (R2) Humans possess logic/reasoning.

Concept / Approach:
Explanations for human sociality typically reference cooperation, interdependence, kin and reciprocal altruism, culture, language, and shared norms—none of which is captured by “selfishness.” Pure cognitive capacity (logic) does not by itself entail gregarious behavior.

Step-by-Step Solution:

Verification / Alternative check:
Classic explanations involve survival benefits of cooperation, division of labour, and cultural evolution—distinct from raw selfishness or abstract logic.

Why Other Options Are Wrong:
(a) and (b) over-assign causal power to single traits; (c) accepts both without justification; (e) is vague and unnecessary.

Common Pitfalls:
Equating “rational” with “social”; assuming selfishness directly yields group living.

Final Answer:
Option D: Neither (R1) nor (R2) is the reason.