Where can Charra and Nitella predominantly be found?

Charra and Nitella, both belonging to the group known as stoneworts, are primarily found in freshwater environments such as ponds, lakes, rivers, and ditches. These filamentous green algae thrive in areas where there is a reliable supply of water, typically in places that are relatively shallow and have adequate light conditions. Their habitat includes nutrient-rich waters where they can grow attached to the substrate, contributing to the aquatic ecosystem by providing oxygen and habitat for other organisms.

The environments listed in the other options do not provide the specific conditions that Charra and Nitella require. For example, mountains and valleys may not consistently have the aquatic environments suitable for these species, while forests and deserts lack the presence of freshwater habitats. Wetlands might support some aquatic plants and algae, but they are not exclusively the habitats for Charra and Nitella, as these species can be found in a broader range of freshwater ecosystems.