Final Answer:
A pathogen is the presence and multiplication of harmful foreign microorganisms in the body. Harmful foreign microorganisms in the body that can cause infections are called pathogens. An infection is a condition that occurs when one or more of the body’s systems, organs, or structures is not working correctly.
Step-by-step explanation:
The correct word to complete the sentences is "pathogens." A pathogen refers to any microorganism (such as bacteria, viruses, fungi, or parasites) that causes disease in its host. The completion provides consistency in the terminology used in the context of microorganisms causing infections.
The completion ensures that the terminology aligns with the definitions and accurately conveys the relationships between pathogens and infections in the given sentences.