[单项选择] Both in what is now the eastern and the southwestern United States, the peoples of the Archaic era (8,000-1,000 B.C) were, in a way, already adapted to beginnings of cultivation through their intensive gathering and processing of wild plant foods. In both areas, there was a well-established ground stone tool technology, a method of pounding (5) and grinding nuts and other plant foods, that could be adapted to newly cultivated foods. By the end of the Archaic era, people in eastern North America had domesticated certain native plants, including sunflowers; weeds called goosefoot, sumpweed, or marsh elder; and squash or gourds of some kind. These provided seeds that were important sources of carbohydrates and fat in the diet. (10) The earliest cultivation seems to have taken place along the river valleys of the Midwest and the Southeast, with experimentation beginning as early as 7,000 years ago and domestication be
A. The principal sources of food that made up their diet
B. Their development of ground stone tool technology
C. Their development of agriculture
D. Their distribution of work between men and women