The flu is an infection caused by a pathogen. when a pathogen enters the body, which blood component us to attack the pathogen?

-White blood cells.

Explanation:

White blood cells (or leukocytes) represent a type of blood cells that provide protection against foreign pathogens and infectious diseases.

These cells include both non-specific immune cells (such as neutrophils and eosinophils) and specific immune cells (T and B lymphocytes). These cells   kill and eliminate pathogens from the body by various mechanisms, such as phagocytosis or substances, such as cytokines and antibodies.

Thus, if a person is infected by flu virus, the blood component that helps him to attack the pathogen would white blood cells.

white blood cells

Explanation:

all of the above

the denominator has a very specific role.