Final answer:
The Sumerians invented plows, calendars, and writing, with their development of cuneiform script marking a major step forward in record-keeping and literature.
Step-by-step explanation:
The Sumerians were not only the first to invent plows and a 12 month calendar, but they also made significant advancements in various fields. One of their greatest inventions was writing, specifically the development of cuneiform. This script, characterized by wedge-shaped symbols, evolved into a phonetic script that had symbols representing syllables. It was initially created for record-keeping but later enabled the creation of true forms of literature.
Moreover, their contributions to agriculture, such as the invention of the plow and the use of irrigation techniques, significantly enhanced the productivity and capabilities of early civilizations.