Wild animals placed in zoos sometimes die shortly thereafter. These deaths are likely to result from a(n)

A) decrease in the animals' production of lymphocytes.
B) increase in the animals' production of oxytocin.
C) decrease in the animals' production of norepinephrine.
D) increase in the animals' production of serotonin.

Placing wild animals in zoos can be a stressful experience, causing a decrease in the animals' production of lymphocytes or white blood cells, which are important for fighting off infections and diseases. This can make them more susceptible to illness and death. Increased production of oxytocin, serotonin, or norepinephrine may be related to behavioral changes in animals in response to their environment, but they are not directly related to their survival or susceptibility to illness.