Q14:
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.
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.
D. The milk of mammals would be less nutritious if it did not
contain cannabinoids.
E. The chemical that blocks cannabinoids from stimulating
their brain receptors does not independently inhibit the appetite.
答案為何是E?而不是B