What describes naturally acquired passive immunity?

Naturally acquired passive immunity occurs when antibodies are transferred from one individual to another, providing immediate but temporary protection against certain diseases. This transfer commonly occurs during pregnancy, when antibodies are passed from the mother to the fetus through the placenta, or through breastfeeding, where antibodies in the mother's milk are ingested by the infant. This type of immunity is important for newborns as it helps to protect them during their early months of life when their own immune systems are still developing.

In contrast, the other options refer to different mechanisms of immunity. The injection of antibodies would represent artificially acquired passive immunity rather than natural transfer. Exposure to a disease would refer to the development of naturally acquired active immunity, where the body itself generates an immune response after exposure to pathogens. The administration of a vaccine is a form of artificially acquired active immunity, as it stimulates the body to create antibodies in response to a safe, yet similar, form of the pathogen.