Question

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?
A. Newborn mice do not normally ingest any substance other than their mothers’
milk. - Irrelevant
B. Cannabinoids are the only substances in mammals’ milk that stimulate the
appetite.
C. The mothers of newborn mice do not normally make any effort to encourage their
babies to feed. - Irrevelant
D. The milk of mammals would be less nutritious if it did not contain cannabinoids. - Irrelevant
E. The chemical that blocks cannabinoids from stimulating their brain receptors does
not independently inhibit the appetite.

Answer 1

B. Cannabinoids are the only substances in mammals’ milk that stimulate the appetite.

Step-by-step explanation:

Note, in logical reasoning, an argument is often based on a particular premise or assumption.

Since we are told the injected mice showed far less interest in feeding than normal newborn mice do after been injected with a chemical known to block cannabinoids, the best assumption that supports this result is that cannabinoids are the only substances in mammals’ milk that stimulates appetite.

In other words, no other substance can result in a lack of or reduced appetite in mammals since the researchers were only concerned with a chemical that blocks cannabinoids from reaching their receptors in the brain so as to prevent stimulation of appetite.