Reading Comprehension
试题详情
文章：
| Line | Anthropologists once thought that the ancestors |
| of modern humans began to walk upright because | |
| it freed their hands to use stone tools, which they | |
| had begun to make as the species evolved a brain of | |
| (5) | increased size and mental capacity. But discoveries |
| of the three-million-year-old fossilized remains of | |
| our hominid ancestor Australopithecus have yielded | |
| substantial anatomical evidence that upright walking | |
| appeared prior to the dramatic enlargement of the | |
| (10) | brain and the development of stone tools. |
| Walking on two legs in an upright posture (bipedal | |
| locomotion) is a less efficient proposition than walking | |
| on all fours (quadrupedal locomotion) because several | |
| muscle groups that the quadruped uses for propulsion | |
| (15) | must instead be adapted to provide the biped with |
| stability and control. The shape and configuration | |
| of various bones must likewise be modified to allow | |
| the muscles to perform these functions in upright | |
| walking. Reconstruction of the pelvis (hipbones) and | |
| (20) | femur (thighbone) of “Lucy,” a three-million-year-old |
| skeleton that is the most complete fossilized skeleton | |
| from the Australopithecine era, has shown that they | |
| are much more like the corresponding bones of the | |
| modern human than like those of the most closely | |
| (25) | related living primate, the quadrupedal chimpanzee. |
| Lucy’s wide, shallow pelvis is actually better suited to | |
| bipedal walking than is the rounder, bowl-like pelvis of | |
| the modern human, which evolved to form the larger | |
| birth canal needed to accommodate the head of a | |
| (30) | large-brained human infant. By contrast, the head of |
| Lucy’s baby could have been no larger than that of a | |
| baby chimpanzee. | |
| If the small-brained australopithecines were not | |
| toolmakers, what evolutionary advantage did they | |
| (35) | gain by walking upright? One theory is that bipedality |
| evolved in conjunction with the nuclear family: | |
| monogamous parents cooperating to care for their | |
| offspring. Walking upright permitted the father to | |
| use his hands to gather food and carry it to his mate | |
| (40) | from a distance, allowing the mother to devote more |
| time and energy to nurturing and protecting their | |
| children. According to this view, the transition to | |
| bipedal walking may have occurred as long as ten | |
| million years ago, at the time of the earliest hominids, | |
| (45) | making it a crucial initiating event in human evolution. |
题目：
The passage suggests that proponents of the theory mentioned in lines 35–38 assume that which of the following steps in human evolution occurred most recently?
选项:
A、Development of a nuclear family structure
B、Transition from walking on all fours to walking upright
C、Dramatic enlargement of the brain
D、Use of the hands to gather and carry food
E、Modification of propulsive muscles to provide stability and control in locomotion
答案:
C
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