Roles of T- and B-Lymphocytes in Immunity Steps:

• T-lymphocytes mediate cell-mediated immunity by directly attacking infected cells.
• B-lymphocytes produce antibodies for humoral immunity against extracellular pathogens.
• The correct row pairs T-lymphocytes with cell-mediated and B-lymphocytes with humoral immunity.
• Option A matches this standard immunological distinction.

Why A is correct:

• T-lymphocytes handle cell-mediated responses, while B-lymphocytes drive humoral responses, as defined in immunology.

Why the others are wrong:

• B: Incorrectly assigns T-lymphocytes to both, ignoring B-cell antibody role.
• C: Wrongly pairs B-lymphocytes with cell-mediated, which requires T-cells.
• D: Falsely attributes humoral immunity to B-lymphocytes twice, omitting T-cell function.

Final answer: A