考研英语模拟试题及答案

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，remarkable findings have been made in ethology，the study of animal social behavior. earlier scientists had 1 that nonhuman social life was almost totally instinctive or fixed by genetics. much more careful observation has shown that 2 variation occurs among the social ties of most species，showing that learning is a part of social life. that is，the 3 are not solely fixed by the genes. 4，the learning that occurs is often at an early age in a process that is called imprinting. imprinting is clearly 5 instinctive，but it is not quite like the learning of humans；it is something in between the two. an illustration best 6 the nature of imprinting. once，biologists thought that ducklings followed the mother duck because of instincts. now we know that，shortly 7 they hatch，ducklings fix 8 any objec考研英语模拟试题及答案

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