What type of immunity is represented by antibodies passed in breast milk?

Antibodies passed in breast milk represent natural passive immunity because this type of immunity involves the transfer of antibodies from one individual to another without the recipient's immune system actively producing them. In this case, a mother produces antibodies in her body in response to pathogens she has encountered and then passes those antibodies to her infant through breast milk. This provides the infant with immediate protection against certain infections during the early months of life.

In contrast, natural active immunity occurs when a person's immune system is exposed to a pathogen, leading to the production of their own antibodies and memory cells. Artificial active immunity involves vaccination, where a person is exposed to a controlled dose of antigens to stimulate an immune response without causing disease. Artificial passive immunity is given through the injection of pre-formed antibodies, typically derived from another individual or animal, to provide immediate, but temporary, protection.

Thus, the correct choice is natural passive immunity because it specifically refers to the transfer of maternal antibodies through breast milk, which is a natural process beneficial for the infant's immune defense.