Final answer:
The written language of everyday speech in a particular region is known as the vernacular. In the context of the provided information, Latin was the written language of everyday speech for the educated elite across Europe, while cuneiform was the standard written language used in ancient Mesopotamia.
Step-by-step explanation:
The written language of everyday speech in a particular region is known as the vernacular. It is the language that is commonly spoken and understood by the people in that region. In the context of the provided information, Latin was the written language of everyday speech for the educated elite across Europe, while cuneiform was the standard written language used in ancient Mesopotamia. Therefore, the correct answer to the question is a) Vernacular.