请教一题GWD

cxks01

The milk of many mammals contains cannabinoids, substances that are known to stimulate certain receptors in the brain.To investigate the function of cannabinoids, researchers injected newborn mice with a chemical that is known to block cannabinoids from reaching their receptors in the brain.The injected mice showed far less interest in feeding than normal newborn mice do.Therefore, cannabinoids probably function to stimulate the appetite.


Which of the following is an assumption on which the argument depends?

1. Newborn mice do not normally ingest any substance other than their mothers’ milk.
   
2. Cannabinoids are the only substances in mammals’ milk that stimulate the appetite.
   
3. The mothers of newborn mice do not normally make any effort to encourage their babies to feed.
   
4. The milk of mammals would be less nutritious if it did not contain cannabinoids.
   
5. The chemical that blocks cannabinoids from stimulating their brain receptors does not independently inhibit the appetite.
   为什么不选B？答案是E
   我想了很久都觉得是B，请帮我分析一下为什么错，谢谢
   

cxks01

非常感谢你的解答，很清晰，现在明白了！

mute800

这题的结论是：因此C物质的作用是引起胃口。
论据是：向新生小老鼠里注射组织C到达大脑部位的物质，和对照组小老鼠相比更没有胃口。
E是说：不是阻止C到达大脑的这种物质独立地抑制了小老鼠的胃口。
也就是说不是这种物质使小老鼠没胃口，而是通过它阻止C到大脑才抑制了胃口。（举个不恰当的例子不是吃了恶心的东西所以没胃口）
你想选的B和这个实验过程是没有关系的，你需要的时和实验联系起来得出结论。