Grafting between two members of the same species is known as:

Which of the following statements is incorrect?

Antibodies in our body are complex of ........

Which cells are responsible for the production of immunoglobulins?

Which organs provide the microenvironment for the maturation of $T$-lymphocytes?

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.