Which of the following plants would you find in a forest?

Ferns, particularly when referring to their reproductive structures known as sori, are commonly found in forest ecosystems. These plants thrive in the moist, shaded environments that forests provide. Ferns reproduce via spores, which are typically found in clusters on the undersides of their fronds, part of the sori. This adaptation allows them to proliferate in forested areas, where they often contribute to the undergrowth and help in the ecosystem's biodiversity.

In contrast, bog cranberries typically grow in wetland areas rather than dense forests, while cattails are commonly found in marshes or along the edges of lakes and streams. Cotton grass is more suited to cooler, wetland environments such as tundras or bogs. Thus, ferns are more representative of forest habitats, making them the most appropriate choice in this context.