Final Answer:
High-affinity neutralizing antibodies that help in protective immunity are predominantly IgG. Option B is the answer.
Step-by-step explanation:
Immunoglobulin G (IgG) is a class of antibodies that plays a crucial role in adaptive immune responses. Among the options provided (IgA, IgG, IgM, IgD), IgG is particularly known for its high affinity and effectiveness in neutralizing pathogens, such as bacteria and viruses. IgG antibodies are produced during the secondary immune response and contribute to long-term immunity by providing protection against specific pathogens.
While other immunoglobulins, such as IgA and IgM, also have important roles in the immune system, IgG is often associated with long-lasting protective immunity. IgA is more commonly associated with mucosal immunity, while IgM is involved in the early stages of an immune response.
Option B is the answer.