Which of the following is a type of erect algae?

Chara is categorized as a type of erect algae, specifically a green algae belonging to the Characeae family. It typically forms dense underwater beds in freshwater environments and is known for its erect growth form, which can resemble a plant due to its stem and leaf-like structures. Chara serves important ecological roles, including providing habitat for aquatic organisms and stabilizing sediments.

In contrast, the other options represent various forms of aquatic vegetation, but they do not fall under the category of erect algae. Watermilfoil is a submerged aquatic plant known for its feathery leaves, while both water lettuce and duckweed are free-floating plants that lack the erect structure typically associated with erect algae. Understanding the characteristics of different types of aquatic plants helps in effective identification and management practices in aquatic ecosystems.