Which of the following best describes the fundamental principle of how most modern vaccines protect people?

Giving a person a tiny dose of a fully infectious pathogen is safe and lets their body build immunity

Presenting a harmless form of a pathogen or a piece of it to the immune system stimulates memory-cell formation without causing disease

Infecting people with a related animal pathogen that causes mild illness gives cross-protection against the human disease

Administering ready-made antibodies provides long-term protection by teaching the immune system to remember the pathogen