[单项选择]　　　 Many prehistoric people subsisted as hunters and gatherers. Undoubtedly, game 　　　 animals, including some very large species, provided major components of human diets. 　　　 An important controversy centering on the question of human effects on prehistoric wildlife 　　　 concerns the sudden disappearance of so many species of large animals at or near the end (5) of the Pleistocene epoch. Most paleontologists suspect that abrupt changes in climate led 　　　 to the mass extinctions. Others, however, have concluded that prehistoric people drove 　　　 many of those species to extinction through over-hunting. In their "Pleistocene overkill 　　　 hypothesis," they cite what seems to be a remarkable coincidence between the arrival of 　　　 prehistoric peoples in North and South America and the time during which mammoths, (10) giant ground sloths, the giant bison, and numerous other large mammals became extinct. 　　　 Perhaps the human species was driving others to extinction long be
A. the effect of climate changes on large game animals
B. large animals moving into a new environment
C. humans hunting some species more than others
D. older animals not being able to compete with younger animals

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