Passive immunity results from the use of:

Passive immunity occurs when a person receives preformed antibodies (or antitoxin) made by another human or animal source. It provides immediate protection, but it is temporary because the transferred antibodies decline over weeks to months. CDC’s Pink Book defines passive immunity as protection by antibody or antitoxin produced by one individual and transferred to another.

Option A (tetanus antitoxin) is a classic example of passive immunization: antitoxin (including human tetanus immune globulin preparations) provides antibodies that neutralize tetanus toxin, giving rapid, short-term protection. CDC’s vaccine best-practices glossary notes that antitoxins are used to confer passive immunity.

In contrast, options B, C, and D are vaccines, which induce active immunity by stimulating the recipient’s immune system to produce its own antibodies and immune memory. That response takes time to develop but is longer-lasting than passive immunity.