Antibodies are ........

Given below are two statements. Select the most appropriate answer from the given options.
Statement-$I$: $T$-lymphocytes have $4$ subtypes as helper,killer,memory,and suppressor $T$-cells.
Statement-$II$: $B$-lymphocytes mature in the thymus and are responsible for cell-mediated immunity.

Which of the following is not a physiological barrier?

How many antigens can each antibody molecule bind to at most?

The immunity developed in the body after recovering from a disease is:

What type of barrier is the mucus coating?