Why does the author include the information that some cave art has been "photographed, but the camera gives a poor idea of their nature and quality?" A. To help explain why lack of access to caves is an obstacle to understanding the Magdalenian art system. B. To suggest that these artworks have suffered less deterioration than has sometimes been claimed. C. To argue that air-conditioning should be installed in the Altamira cave in Spain. D. To emphasize the need to view these artworks while lying down.