Why does the author say that "many such tools show signs of long, intensive use" in connection with Natufian agriculture? A. To argue that the Natufian people consumed grains long before they included fish in their diet B. To suggest that Natufian people could not replace their tools frequently because they had to travel very long distances to find grinding stones C. To illustrate the sophistication of the Natufians in the design of stone tools D. To support the claim that the archaeological record of the Natufian period shows clear evidence of agricultural origins