In mammals it is the secondary palate that permits breathing while eating. Clear

游客2024-01-13  7

问题 In mammals it is the secondary palate that permits breathing while eating. Clearly, breathing while eating is necessary to maintain the high rate of metabolism of mammals. The author’s assertions would be most weakened by the discovery of a mammalian species that had a______.

选项 A、high rate of metabolism and the ability to breathe while eating
B、low rate of metabolism and the ability to breathe while eating
C、low rate of metabolism and no ability to breathe while eating
D、high rate of metabolism and no secondary palate
E、low rate of metabolism and a secondary palate

答案 D

解析 我们不妨用A表示“上颚”,B表示“进食时呼吸”,C表示“维持高频率的新陈代谢”。本题段落的第一句话只表明上颚使哺乳动物进食时呼吸,但确定结论“哺乳动物进食时呼吸”的成立需要依赖于很多条件,而上颚仅仅是使这个确定结论成立的一个必要条件,所以由A绝对推不出B;但是B既然存在,就必然可以得出A这个必要条件是存在的,因为没有A就没有B,所以第一句话的推理可以表示为B→A。段落的第二句话中的“is necessary to”表示B为C的一个必要条件,可表示为C→B.所以整个段落的推理可表示为C→B→A。这种推理的答案大多考察C→A。(D)指出C与A同时存在,与C→A相反,所以起到了反对作用,所以(D)正确;(B)、(C)、(E)中的“low rate of metabolism”是C,作为否命题与原命题无关;(A)与C→A完全吻合,所以不可能起到反对作用。
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