The correct answer is option 2: urban. The Harappans were an ancient civilization that existed in the Indus Valley (modern-day Pakistan and northwest India) around 2600-1900 BCE. They were known for their well-planned urban centers, such as Mohenjo-daro and Harappa, which had sophisticated infrastructure, including a grid-like street system, a centralized drainage system, and multi-story houses.

Option 1 (rural) is incorrect because the Harappans lived in organized and developed cities, rather than rural areas. Option 3 (nomadic) is also incorrect since nomadic societies typically do not settle in permanent urban centers. Option 4 (tribal) is not accurate as the Harappans had complex social and political systems, and their society was more centralized and organized than a tribal society.

Therefore, option 2 (urban) is the correct answer.