The correct answer is D) They developed water management that included drainage systems.
The Harappan planners responded to flooding from monsoon season in that "They developed water management that included drainage systems."
We are talking about one of the most ancient human civilizations, the Indus River Valley culture that settled in next to the Indus River in the region of Indian and Pakistan. They developed great agriculture techniques to benefit from the fertile soil of the banks and produce many cash crops to feed their families as well as for trade. The Harappans had good plans to develop water management that included drainage systems that benefited their cities and prevented flooding.
The Harappan people also developed maritime and land trade routes to the region of the Middle East, modern-day Iran, Syria, and Iraq.