Which of the following refers to the invasion and multiplication of microorganisms in body tissues?

The correct answer is infection, which refers to the process where microorganisms such as bacteria, viruses, fungi, or parasites invade and multiply within body tissues. This can lead to an array of symptoms and health issues, as the invading organisms can disrupt normal bodily functions and provoke immune responses.

Infection can occur through various routes, including direct contact, inhalation, or ingestion, and it often necessitates medical attention, depending on the severity and type of microorganisms involved.

The other terms listed have distinct meanings that do not align with the definition of invading and multiplying within body tissues. Infestation refers specifically to the overgrowth of parasites on or within a host, immunization indicates the process of making a person or animal immune to infection, usually through vaccines, and inoculation involves the introduction of a pathogen into a host to induce an immune response, but it does not imply multiplication and invasion are already occurring in tissues.