Which antibody is present in the highest concentration in mother's milk?

Match the columns:

Column-$I$	Column-$II$
$(a)$ Main lymphoid organ	$(1)$ Thymus
$(b)$ $MALT$	$(2)$ Spleen
$(c)$ Lobe-like organ arranged near heart	$(3)$ Bone marrow
$(d)$ Large bean-shaped organ	$(4)$ It constitutes $50\%$ of lymphoid tissue

Recognition and digestion by the phagocytes due to the coated surface of antigens by the antibodies is known as

Which of the following is a primary lymphoid organ?

When a host is exposed to antigens,which lead to the production of antibodies in the host body,this type of immunity is called:

What is an allograft?