Final answer:
Agriculture allowed hunter/gatherer groups of humans to build large cities by providing a surplus of food, leading to population growth, labor specialization, and the establishment of organized communities.
Step-by-step explanation:
The development that allowed hunter/gatherer groups of humans to build large cities was agriculture. The transition from nomadic hunt-and-gather groups to more complex societies based on agriculture allowed for the development of sedentary cultures, establishment of governments, writing and number systems, and hierarchal social systems. Agriculture provided a surplus of food, which in turn led to population growth, labor specialization, and the establishment of organized communities, ultimately leading to the construction of large cities.