The answer is d I juss took the test
Because predators and prey must learn (or adapt) new ways of survival. Deer over time have learned to be much more sensitive to the surrounding environment, therefore, a deer's predator must also adapt/evolve and learn how to beat the deer at it's own game and catch it for food. Animals must evolve/adapt to any given environment. If humans lived in Antarctica for thousands of years, we would eventually be able to withstand the cold due to evolution. People who live in the Himalayas today actually breath normally at such high altitudes whereas if someone who lives at sea level went to where the Himalayan people lived, the result could potentiality be fatal because the body has not adapted/evolved at that point to withstand minimal oxygen.
Ghrelin INCREASES APPETITE.
Ghrelin is an hormone which is majorly produced by the stomach. Other organs, which produces the hormone in small quantities include: the brain, the pancreas and the small intestines. The hormone has many functions, but its major function is to stimulate appetite, increase food intake and to promote fat storage.