参考答案

正确答案：D
解析：细节题型见第一段第一句：Ever since it was claimed that a medicine made from the Chinese three—striped box turtle could cure cancer，demand for the product has increased，making the turtle the most expensive to be found in China's food markets．(自从声称用中国产三线箱龟[金钱龟]制成的药物能治疗癌症后，对金钱龟的需求大量增加，这使得金钱龟在中国食品市场上成为最昂贵的东西)；因此D为答案(它们之所以昂贵是因为它们的药用价值)。