Which type of microorganisms can be classified as pathogens?

Pathogens are microorganisms that can cause disease in a host organism. The correct answer encompasses a wide variety of microorganisms that are known to be responsible for infections and diseases in humans and other living organisms.

Viruses are a class of pathogens that invade host cells and replicate, often causing illnesses such as the flu or COVID-19. Bacteria, which can be both beneficial and harmful, are responsible for conditions ranging from mild infections to severe diseases, such as strep throat or tuberculosis. Fungi, including yeasts and molds, can also be pathogenic; for example, they can lead to infections like athlete's foot or more serious systemic infections in immunocompromised individuals. Protozoa are single-celled organisms that can cause diseases like malaria and amoebic dysentery.

This selection underscores the diversity of pathogens, reflecting the complexity of infectious diseases. The other options do not capture the full range of microorganisms that can act as pathogens, limiting the understanding of how different types of microbes contribute to disease processes.