Assertion–Reason (Indus Valley Civilization):\nAssertion (A): Indus Valley people knew the art of navigation.\nReason (R): Indus seals and artifacts indicate the prevalence of overseas trade.

Introduction / Context:
This item concerns archaeological inference: whether material evidence of long-distance trade supports knowledge of navigation among Indus Valley people.

Given Data / Assumptions:

• Artifacts and seals imply trade links with Mesopotamia and other regions.
• Assertion claims knowledge of navigation.

Concept / Approach:
Evidence such as dockyards (Lothal), standardized weights, seals, and imported/exported materials points to organized commerce, likely including maritime trade. Maritime commerce, in turn, implies practical navigation knowledge sufficient for coastal voyages and possibly open-water segments.

Step-by-Step Solution:
1) A: True—archaeological context supports practical navigation for trade.2) R: True—seals and port structures indicate overseas/commercial connectivity.3) R gives the evidentiary basis for A, so it explains the assertion.

Verification / Alternative check:
Lothal’s dock-like structure and trade records align with maritime activity, a proxy for navigation skills.

Why Other Options Are Wrong:
Denying either statement contradicts archaeological consensus; denying explanatory link ignores that overseas trade presupposes navigation competencies.

Common Pitfalls:
Overstating sophistication (e.g., celestial navigation) versus practical coastal navigation; the assertion requires only practical capability.

Final Answer:
Both A and R are true, and R explains A.