What type of algae resembles the appearance of hair?

The choice of filamentous algae is correct because this type of algae grows in long, hair-like strands, giving it a distinctive appearance that resembles hair. Filamentous algae commonly thrive in freshwater environments, where they can form large mats or tufts that may float or attach to submerged surfaces. Their structure is characterized by thin filaments or strands, which is why they can be visually identified as having a "hairy" look.

Other types of algae and plants mentioned in the choices have different characteristics. Chara and Nitella are categorized as green algae but typically appear more like moss or stiff vegetation rather than hair-like strands. Watermilfoil is an aquatic plant with finely divided leaves that may seem feathery but does not have the same filamentous appearance as filamentous algae. Understanding these distinctions helps in identifying and managing aquatic pests effectively.