Final answer:
Stress can lead to increased vulnerability to infections and immune deficiency disorders.
Step-by-step explanation:
The statement that BEST describes the effects that stress has on the immune system is A. Stress can lead to increased vulnerability to infections and immune deficiency disorders.
When a person is stressed, their body releases stress hormones that can suppress the immune system. This makes the person more susceptible to infections, illness, and immune deficiency disorders.
For example, chronic stress has been linked to an increased risk of developing conditions like asthma, allergies, and autoimmune diseases.
Learn more about Effects of stress on the immune system