How is passive immunity typically acquired?

Passive immunity is typically acquired through the transfer of antibodies from one individual to another, which is most commonly seen in the context of maternal antibodies. When a mother provides her offspring with antibodies, usually through the placenta during pregnancy or via colostrum after birth, the young animal gains immediate protection against pathogens without having to produce its own antibodies. This form of immunity is crucial in the early stages of life when the infant's immune system has not yet had the chance to encounter and respond to infections.

The other options represent different forms of immunity or exposure. Vaccination leads to active immunity, where an organism's own immune system is stimulated to produce antibodies. Natural infection also results in active immunity as the body responds to actual pathogens. Environmental exposure involves encountering pathogens in the surroundings and does not guarantee immediate protective antibodies like passive immunity does.