Which of the following best describes a pathogen?

A pathogen is best described as a disease-causing organism, which can include various types of microorganisms such as bacteria, viruses, fungi, and parasites. These organisms can invade host organisms—plants, animals, or humans—and lead to harmful effects, including disease. Understanding the role of pathogens is fundamental in various fields, including agriculture, human health, and environmental science, as it helps in the identification of diseases and the development of control measures. In the context of pest management, recognizing what constitutes a pathogen is crucial for effective management practices to prevent and control diseases in crops and livestock.