Which structure in bacteria is used for movement and is often described as a tail?

• A. Cilia
• B. Pus
• C. Active stage
• D. Flagella

Answer: (D)

Bacterial movement is driven by a tail-like appendage called a flagellum. This structure spins like a tiny propeller, pushing the cell through liquid so the bacterium can swim toward favorable conditions (and away from harmful ones). The flagellum is specifically built for propulsion, which is why it’s described as a tail.

Cilia are hair-like projections found on many eukaryotic cells and move in coordinated waves, not typical of bacteria. Pus is not a cellular structure, and an active stage is not a physical part of a bacterium. So the tail-like propulsion provided by the flagellum is the correct concept for how bacteria move.