Final answer:
In Mesopotamia, the most common type of document found is records of business transactions, written on clay tablets using cuneiform writing.
Step-by-step explanation:
The types of documents frequently encountered in the writings recovered in Mesopotamia include records of business transactions, royal inscriptions, law codes, treaties, and literature. Specifically, these documents were often inscribed on clay tablets using cuneiform writing, which was invented by the Sumerians as one of the first systems of writing around 3000 BCE.
Cuneiform started as a pictographic system and eventually included syllabic symbols. These tablets housed a vast array of records, such as receipts, contracts, letters, and incantations, providing insights into the social, religious, and economic life of Mesopotamia.