In the figure,the structure of an antibody molecule is shown. Name the parts $A$,$B$,and $C$.

Which of the following types of tissue grafts will be most successful?

The antibodies are formed in

Given below are two statements:
Statement $I$: Bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced.
Statement $II$: Both bone marrow and thymus provide micro-environments for the development and maturation of $T$-lymphocytes.
In the light of the above statements,choose the most appropriate answer from the options given below:

What does $PMNL$ stand for?

Define Antigen and Antibody. Name any two diagnostic kits based upon them.