Final answer:
Phagocytes are part of the body's second line of defense, functioning to engulf and digest invading pathogens through phagocytosis.
Step-by-step explanation:
The part of the second line of defense against microorganisms from the options provided is A) phagocytes. Phagocytes are part of the innate immune response that attacks pathogens which manage to enter the body. They are nonspecific leukocytes that have the ability to engulf and digest invading pathogens through a process known as phagocytosis. This response is a generalized and nonspecific set of defenses against a class or group of pathogens that include the inflammatory response and showing how our bodies function like a protective fortress against invading microorganisms.