Which of the following is classified as an annual aquatic weed?

The classification of annual aquatic weeds is based on their life cycle and growth habits. Annual plants typically complete their life cycle within a single growing season, germinating from seeds, growing, flowering, and then dying before the onset of the next growing season.

The correct answer is Naid, which includes several species, such as Naiad, that are categorized as annual aquatic plants. Naiad plants often thrive in shallow waters and can regenerate quickly due to their fast growth and seed production. This growth pattern allows them to establish themselves effectively within a growing season and can lead to dense populations under favorable conditions.

On the other hand, Pondweed, Common Elodea, and Arrowhead usually display growth habits that allow them to survive through multiple seasons. For instance, Pondweed and Common Elodea are often perennial, persisting through winter by surviving in rhizomes or other structures. Arrowhead (or Sagittaria) also tends to be perennial, found in wetlands and around ponds, often sending up new shoots year after year. Understanding these classifications is crucial for effective management and control of aquatic plants in various settings.