The Human Microbiome Is Considered an Important Component of the First

The human microbiome is considered an important component of the first line of defense.  Which statement adequately reflects its role as a defensive barrier?

A) The human microbiota competes with pathogens for space and nutrients limiting their ability to cause infection,and trains the immune system to recognize antigens.
B) The organisms that comprise the microbiota are able to phagocytose potential pathogens,thereby eliminating them from the human host.
C) The human microbiome has evolved with the species so it is able to actively destroy pathogens by raising the body temperature when an infection by a pathogen occurs.
D) Cells in the human microbiome secrete cytokines that play a role in stimulating the immune response when a pathogen has entered the system.