Final answer:
The cities of Harappa and Mohenjo-daro depended on the Indus River valley for c. fertile farmland. Their civilization thrived due to the fertile plains and abundant water, which supported agriculture and advanced urban development.
Step-by-step explanation:
The cities of Harappa and Mohenjo-daro depended heavily on the Indus River valley for various aspects of their civilization. However, when referring specifically to the significant natural resource that benefited them, the cities utilized the fertile surrounding land for their agricultural needs. Hence, the correct option is c. fertile farmland. This reliance on agriculture was a foundation of their economy and sustenance.
The Harappan civilization flourished thanks to the fertile plains and abundant water of the Indus River, allowing them to develop advanced urban planning and agricultural techniques. These innovations facilitated the growth of large urban centers like Harappa and Mohenjo-daro, supporting a highly specialized labor force and contributing to the civilization's overall complexity and success.