The correct answer is 3.

 Key Points

Bacterial flagella:-

• Bacterial flagella are complex organelles that play a crucial role in bacterial motility.
• They are composed of three main components:
  • Basal body:
    • The basal body is a complex molecular machine that serves as the rotary motor responsible for flagellar rotation.
    • It is embedded in the bacterial cell envelope and consists of four ring structures (MS, S, C, and P rings) and the rod, which extends into the cell cytoplasm.
  • Hook:
    • The hook is a flexible, curved structure that connects the basal body to the filament.
    • It allows for changes in the flagellum's direction of rotation, enabling the bacterium to maneuver effectively.
  • Filament:
    • The filament is a long, helical structure that extends from the hook and serves as the propeller that propels the bacterium through its liquid environment.
    • It is composed of thousands of copies of a single protein subunit called flagellin.