Which version has a consistent point of view?

A. The history of English is divided into three periods. You could mark the earliest one at about the fifth century A.D.

B. You can say that the history of English could be divided into three periods, and I know the earliest one begins about the fifth century A.D

C. The history of English is divided into three periods. The earliest one begins at about the fifth century A.D.

D. I learned that the history of English is divided into three periods and that you begin the earliest one at about the fifth century A.D.