求助CR一题！in mammals it is the ...

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 mamalian species that had a:

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

D。

E是迷惑项。因为考虑到上颚如果有病，不能发挥作用，则可能会引起低新陈代谢，所以不好说是支持还是削弱。

不知道对否？

D正解

no sp，no breathing，有high rate 说明b不是必须的，weaken！

D选项没有palate并不能说明mammals就不能边吃边呼吸了，也许有其他的器官能让他边吃边呼吸进而有高的新陈代谢率，不能削弱作者的assertion：Clearly, breathing while eating is necessary to maintain the high rate of metabolism of mammals.

反而B选项B  low rate of metabolism and the ability to breathe while eating，就很直观的削弱了。

所以我认为选B

楼上的妹妹把充分跟必要搞反了吧

作者说 Bwe这种行为对于保持high rate是必须的 ，而不是说Bwe就一定能推出有high rate。

谢谢all楼上同学

D正解

我觉得2楼说的有道理，有palate只是high matabolism的一个必要条件

自我总结：如作消弱，只能对必要条件下手，因充分条件是完美充分的