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This evolution of human brains was not without

2022-08-05 15:03:19 问答库阅读 169 次

问题详情

This evolution of human brains was not without its difficulties for mothers, because ______.
A．human brains started to grow larger
B．our ancestors walked upright on two legs
C．it altered our ancestors" skeletons
D．it makes the passage of big-brained infants difficult

参考答案

正确答案：D
解析：参见文中第3段，其大意是，人类进化为两足动物逐渐改变了我们祖先的骨骼。与此同时，头向上倾，骨盆的形状改变，以适应垂直的行走姿势。其结果是产道的一部分变窄，这使得人头婴儿越来越难顺产。故D为正确答案。