What distinguishes Eurasian water milfoil from other aquatic plants?

Eurasian water milfoil is characterized by its distinct morphology, which includes having four feather-like leaves arranged in whorls at each node along the stem. This unique leaf structure differentiates it from many other aquatic plants that typically possess broader leaves. Additionally, the dark reddish stems contribute to its identification, as this feature is not common in many native or non-invasive aquatic plants.

The other options do not accurately describe features of Eurasian water milfoil. For example, broad, flat leaves are more representative of other aquatic plants, and while some plants do produce edible fruit, this is not a defining characteristic of Eurasian water milfoil. Furthermore, the species thrives in freshwater environments rather than saltwater, making the notion of it being exclusive to saltwater habitats incorrect. Thus, the distinct four feather-like leaves and dark reddish stems are what set Eurasian water milfoil apart, establishing its identification in aquatic settings.