Which of the following best defines "waterfowl"?

The definition of "waterfowl" specifically encompasses a group of birds that are commonly found in wetland areas and are adapted to aquatic environments. Ducks, geese, coots, and mergansers are all included in this category. These species share similar characteristics such as webbed feet, which assist in swimming, and a diet that often consists of aquatic plants, insects, and small fish.

While the other options mention various aspects of birds near water, they do not accurately capture the comprehensive range represented by the term "waterfowl." For example, limiting the definition to just geese and swans excludes the other significant categories of waterfowl such as ducks. Describing waterfowl only as migratory birds or as all birds living near water broadens the definition incorrectly, as not all birds that live near water are classified as waterfowl, and many species of waterfowl are non-migratory as well. Thus, the choice that specifies ducks, geese, coots, and mergansers is the most accurate representation of what constitutes waterfowl.