According to paragraph 4, how did the Akkadians use the Sumerian language? A. They used Sumerian for speaking but used their own national language for writing. B. They used the complex cuneiform signs developed by the Babylonians and Assyrians rather than the Sumerian signs. C. They developed their own cuneiform shapes on clay tablets to replace those used by the Sumerians. D. They assigned new sound and word values to the signs of Sumerian cuneiform.