Step 1: Verify Statement A: Harappan sites have yielded Mesopotamian seals, and Mesopotamian texts mention trade with 'Meluhha' (identified with the Indus region) — confirming extensive trade with contemporary Bronze Age civilizations.
Step 2: Verify Statement B and the link: Bronze Age civilizations (Harappa, Mesopotamia, Egypt) all depended on long-distance exchange for tin, copper, lapis lazuli, carnelian, etc., since these raw materials were not locally available everywhere — this exchange dependency is exactly why extensive trade networks existed, so B correctly explains A.
Final Answer: Option (i) — both correct, B correctly explains A.