A key virulence factor of *Staphylococcus aureus* that inhibits opsonization and phagocytosis by binding to the Fc portion of IgG antibodies is:

✓ Correct Answer: Option C

Protein A on the surface of *Staphylococcus aureus* binds to the Fc region of IgG, preventing antibodies from acting as opsonins and thus inhibiting phagocytosis by macrophages and neutrophils.