Answer: A. Neutrophils gather at the site of infection and release histamin, while macrophages ingest antigens before they enter the bloodstream.
Explanation:
Neutrophils are specialized white blood cells which are capable of fighting against the infections. Neutrophils are required at the site of injury and produces histamin to fight against inflamation. Whereas the macrophages are type of monocytes that ingest foreign antigens or bodies like bacteria and virus which could enter the bloodstream and cause disease oriented symptoms.