Which of the following statements is not true about the Indus Valley civilization? A. The Indus Valley farmers grew a surplus of wheat, barley, and a variety of fruits. B. The people of the Indus Valley invented a complex system of writing. C. Almost all the people of the Indus Valley were farmers. D. Many cities grew up in the valley of the Indus River, including Harappa and Mohenjo-Daro.