Final answer:
The development of agriculture can be considered the most significant in ancient Mesopotamia, as it laid the foundation for other key developments, including writing, transportation, and irrigation systems.
Step-by-step explanation:
The most significant development in ancient Mesopotamia is a subject that encompasses several key areas. Given the choices provided, the development of writing stands out as one of the most transformative, as it enabled the recording of transactions, laws, and stories, allowing civilization to advance in terms of administration, culture, and record-keeping. Agriculture, however, can be considered the foundation that supported all other developments, as it led to the rise of food surpluses, specialized labor, and the organization of societies.
Developments in transportation, such as the invention of the wheel and chariots, greatly facilitated trade and mobility, reinforcing the interconnectivity of the region and contributing to its economic and cultural expansion. Lastly, irrigation technology was a critical advancement enabling the control and distribution of water resources, which was essential for sustaining agriculture in the arid landscape of Mesopotamia.
Considering the historical impact and foundational role of each, it is challenging to single out just one development, but it can be argued that without the ability to cultivate land and manage water through irrigation, the other developments might not have been possible.