Which of the following is a feature of passive acquired immunity?

• A. Activated by exposure to antigens
• B. Antibodies are provided and not produced by the host
• C. It develops slowly over time
• D. It requires actual infection to provide immunity

Answer: (B)

Passive acquired immunity is characterized by the transfer of antibodies from one individual to another, rather than the production of antibodies by the host's immune system. In this form of immunity, the host receives preformed antibodies, which are usually obtained from maternal sources through the placenta or breast milk, or from immunoglobulin therapies. This results in immediate but temporary protection against specific pathogens, as the recipient's immune system does not generate its own antibodies.

The other options describe aspects that do not apply to passive acquired immunity. For instance, active immunity is dependent on exposure to antigens, which involves the host's immune system responding to a pathogen by producing its own antibodies and memory cells. This process often takes time to develop. Similarly, acquiring immunity through actual infection is related to active immunity, where the host's body mounts a response that fosters long-term protection, contrasting with the immediate, yet transient, effects seen in passive immunity.