How is the skin the body's first line of defense?

a. It secretes oil, which washes away pathogens.
b. It secretes sweat, which raises the pH of the skin and kills pathogens.
c. It forms a physical barrier to keep pathogens out.
d. It traps pathogens in the many flagella that line mucous membranes.

b. It secretes sweat, which raises the pH of the skin and kills pathogens is the correct answer.

Explanation:

The first line of defense such as skin, mucus, tears, urine flow protects from the pathogens and prepare to protect the body from germs and infections.

Skin secretes swear that raise the pH makes the sweat acidic and then the sweat present in the skin provide protection to the body by killing the unwanted pathogens as some pathogen are not able to survive in acidic conditions.

Skin secretes sweat that contains a chemical dermcidin that breaks the bacteria and kills the pathogens.

unicellular

A.absence of well-differentiated tissue and organ