Match the following barriers of innate immunity with their respective examples and select the correct option:

List-$I$ (Barrier)	List-$II$ (Example)
$A$. Physical barrier	$i$. Skin
$B$. Physiological barrier	$ii$. Interferons
$C$. Cellular barrier	$iii$. Mucus coating
$D$. Cytokine barrier	$iv$. Saliva in mouth

Which of the following organs provides the sites for interaction of lymphocytes with the antigen?

Which of the following statements are correct regarding the structure and types of antibodies in humans?
$i$. Antibodies are also called Immunoglobulins that are produced as an immune response to antigenic stimulation.
$ii$. They are produced by all types of $T$-lymphocytes and $B$-lymphocytes.
$iii$. An antibody is a $Y$-shaped molecule formed of four polypeptide chains. Antibodies present in plasma determine many blood group systems like $ABO$,$Rh$,$P$,$MNS$ etc.
$iv$. An antibody molecule consists of two antigen-binding sites called paratopes.

Helper $T$-cells : Lymphokines :: Killer $T$-cells : . . . . . . .

Antibodies are produced by

The figure given below shows an antibody molecule. Name the parts $A, B$ and $C$.