A significant contribution of Marx and Engels to the study of demography is the suggestion that __________. A. poverty, not overpopulation, is the central issue relating to food supply in a capitalist economy B. population grows exponentially but food supply grows arithmetically, thereby creating a doubling effect C. population explosion would eventually be checked by mortality risks, such as natural and man-made disasters D. the greatest crisis today facing low-income nations is food shortage, not capital shortage