Which of the following is a common emergent weed?

Cattails are classified as common emergent weeds because they grow in wetland areas and extend above the water surface. They typically thrive in shallow waters and can establish dense stands that may alter natural habitats and ecosystems. Emergent vegetation like cattails plays a significant role in providing habitat for wildlife, stabilizing shorelines, and filtering water, but they can become problematic if they proliferate excessively, displacing other native species and leading to reduced biodiversity.

In contrast, water lettuce and duckweed are considered floating aquatic plants, meaning they float on the surface of the water, while algae are microscopic organisms that can bloom in water bodies but do not have a conventional plant structure like emergent weeds. These distinctions are important to understand the ecological roles and management strategies relevant to aquatic environments.