What is a common characteristic of nonpathogenic organisms?

Nonpathogenic organisms are primarily characterized by their beneficial nature. These organisms play vital roles in various ecosystems, including aiding in digestion, contributing to soil health, and even protecting against harmful pathogens by outcompeting them. For example, many types of bacteria found in the human body fall into this category; they help maintain a healthy balance in the microbiome, support the immune system, and prevent the colonization of harmful bacteria.

The other options focus on attributes that do not accurately define nonpathogenic organisms. While some nonpathogenic organisms are microscopic, not all of them are, as there are larger forms like certain plants and fungi that can also be nonpathogenic. The assertion that they come from humans misrepresents their nature; nonpathogenic organisms can be found universally in various environments, not limited to human association. Lastly, stating that they cause illness is fundamentally incorrect, as this characteristic directly opposes the definition of nonpathogenic organisms, which are known for being harmless or even beneficial to health.