Final answer:
IgG is the Ig class associated with Memory. It is the main antibody of secondary responses and provides passive immunity during pregnancy.
Step-by-step explanation:
IgG is the Ig class that is associated preferentially with Memory. IgG is a major antibody of late primary responses and the main antibody of secondary responses in the blood. It is the most abundant antibody class in human blood, accounting for about 80% of total serum antibody.
IgG has the ability to cross the placental barrier, providing passive immunity to the developing fetus during pregnancy.