Which of the sentences below best expresses the essential information in the highlighted sentence in the passage? Incorrect choices change the meaning in important ways or leave out essential information. A. Sumerian script, the earliest known form of writing among prehistoric writing systems, was first used on clay tablets for accounting purposes. B. Although the earliest Sumerians engaged in commercial activity and practiced accounting, they were not as literate as people in other parts of the prehistoric world. C. Archaeologists have discovered that literacy was developed in several parts of the world, including ancient Mesopotamia. D. Archaeological detective work has revealed the commercial accounting practices of the Sumerians of ancient Mesopotamia and provided a written record of their intense commercial activity.