The correct answer would be that bacteria provides vitamins to humans.
<u>By definition, mutualism is a type of symbiotic relationship between two organisms in which both benefit from each other.</u>
Bacteria in the gut of humans that provides vitamins to humans also benefit by making the human gut their shelter. While the vitamins represent an important nutrient to humans for their proper functioning, the shelter is also necessary for the bacteria for their safety.
<em>Hence, the observation that bacteria provide vitamins to humans is consistent with the argument of researchers that some bacteria found in the human gut are in a mutually beneficial relationship with humans.</em>
Animals cause erosion in other ways too. When too many animals live in one place, they tend to eat and trample all the plants. Without the plants to protect the soil, it is much more likely to be eroded by wind and water. Animals cause weathering and erosion on rocky shorelines.
