Final answer:
Babies fed breast milk are protected by passive immunity, as they receive antibodies directly from their mothers through breast milk, which provides temporary protection against infections.
Step-by-step explanation:
The type of immunity that protects a baby who is fed breast milk is passive immunity. This form of immunity does not require the baby to produce its own antibodies; instead, the baby receives protective antibodies from the mother. These antibodies are naturally passed to the baby through breast milk and the placenta during pregnancy, providing the infants with immediate, temporary protection against pathogens.Naturally acquired passive immunity helps protect young infants from common pathogens while their own immune system is still developing. The antibodies like Secretory Immunoglobulin A (IgA) in breast milk provide crucial protection to infants against infections. Once these antibodies are received by the baby, they are effective for a limited time, during which the infant's own immune system matures and takes over the role of fighting against infections.