MDRAO Practice Exam 2025 – Complete Exam Prep Resource

The statement that most microorganisms are harmless to humans is accurate because a significant portion of microorganisms exists within the human microbiome and plays essential roles in maintaining health. These microorganisms can help with digestion, protect against harmful pathogens, and support the immune system. While there are pathogenic microorganisms that cause diseases, the majority of microorganisms present in various environments—including on the skin and within the gut—are either beneficial or neutral to human health.

In contrast, saying that all microorganisms are pathogens is misleading since only a small fraction of microbial life is pathogenic. The assertion that only multicellular organisms can be pathogenic is also incorrect because many pathogens, such as bacteria and viruses, are unicellular or acellular. Lastly, stating that pathogens cannot survive without a host overlooks the fact that many pathogens, particularly bacteria, can survive independently in the environment for extended periods before infecting a host. Thus, the claim that most microorganisms are harmless to humans highlights the distinction between pathogenic and non-pathogenic microorganisms in a balanced manner.