What are microorganisms?

Microorganisms refer to microscopic living organisms that encompass a diverse array of life forms, including bacteria, viruses, fungi, and protozoa. The defining characteristic of microorganisms is their size; they are not visible to the naked eye and typically require a microscope for observation. This characteristic allows them to thrive in a wide range of environments, including extreme conditions where larger organisms may not survive.

The option stating that microorganisms are "microscopic living cells found almost everywhere" accurately captures the essence of microorganisms and their ubiquitous nature. They inhabit soil, water, air, and even the human body, playing crucial roles in processes such as decomposition, fermentation, and even human health.

In contrast, the other options describe aspects related to microorganisms but do not accurately represent them. For instance, defining them as "visible living cells" or suggesting that they are "large organisms" misrepresents their fundamental characteristics. Similarly, stating that they are "only harmful pathogens" overlooks the vast majority of microorganisms that are benign or beneficial, emphasizing that not all microorganisms are harmful.