<span>Larry is taking a walk in the park. The pollen in the air makes him sneeze constantly. The line of defense that is his immune system exhibiting is that of "(A) f</span>irst line of defense." There are only 3 lines of defense in the immune system. The first line of defense <span>are a combination of physical and chemical barriers that prevent all types of foreign agents from penetrating the outer layer of the body. In this case, it is the nasal cavity.</span>
The immune system can be divided into three basic lines of defense against pathogenic infection. The first line of defense (or exterior defense mode) involves physical and chemical restraints that are perpetually willing and equipped to protect the body from germs. These contain your skin, cracks, excretion, cilia, belly acid, urine flow, 'friendly' bacteria and white blood cells known as neutrophils.
Aerobic exercises get your heart rate higher and in turn cause it to work more efficiently while you are resting. Exercises such as running, cycling, swimming are great examples.
