The correct answer is number one: <em>Filamentous rotating structures that provide motility may be singular, paired or scattered.</em>
Explanation:
Flagella are organelles defined by function rather than structure.
The primary function is that of locomotion but also being sensitive to chemicals and temperatures outside the cell.
Helicobacter pylori is a good example of flagella: It uses multiple flagella to propel itself through the mucus lining to reach the stomach epithelium.
Sperm cell is a good example, which uses its flagellum to propel itself through the reproductive tract of females.
1. filamentous rotating structures which porvide motility, may be singular, paired or scattered.
Explanation:
"Bacterial flagella are helically shaped structures containing the protein flagellin. The base of the flagellum (the hook) near the cell surface is attached to the basal body enclosed in the cell envelope. The flagellum rotates in a clockwise or counterclockwise direction, in a motion similar to that of a propeller."
Reference: Britannica, The Editors of Encyclopaedia. “Flagellum.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 2019
