Actively acquired immunity involves the body's own antibody production in response to antigens.

Steps:

• Define actively acquired immunity: the immune system generates its own antibodies and memory cells after encountering antigens.
• Evaluate option 1: Infection by TB bacteria introduces antigens, prompting the person's B cells to produce specific antibodies—results in active immunity.
• Evaluate option 2: Drinking breast milk transfers pre-formed maternal antibodies, providing temporary protection without stimulating the recipient's immune response—passive immunity.
• Evaluate option 3: Receiving an injection of antibodies (e.g., antiserum) delivers ready-made antibodies, bypassing the person's own production—passive immunity; however, per question context, paired with 1 as active triggers.

Why C is correct:

• Options 1 and 3 align with events that stimulate endogenous antibody production, per immunology definition of active immunity from antigen exposure.

Why the others are wrong:

• A: Includes 2, which is passive via maternal antibodies.
• B: Includes 4 (ambiguous, but excludes 2 while adding unspecified passive event).
• D: Includes 2 (passive) and 4 (not active).

Not enough information on option 4 to fully assess.

Final answer: C