**Core Concept**
Tumbling motility is a type of flagellar motion exhibited by certain bacteria, characterized by a rapid, end-over-end movement of the flagellum. This unique motility pattern is a result of the flagellar rotation and is often used as a diagnostic feature in microbiological identification.

**Why the Correct Answer is Right**
The correct answer is associated with the bacterium *Campylobacter jejuni*, which exhibits tumbling motility due to its unique flagellar structure. The flagellum of *C. jejuni* possesses a spiral hook that allows for the rapid rotation and end-over-end movement, enabling the bacterium to move in a characteristic tumbling motion. This motility pattern is a key feature in the identification of *C. jejuni* and distinguishes it from other bacteria.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not correspond to a bacterium known for tumbling motility.
**Option B:** This option is incorrect as it refers to a type of motility exhibited by bacteria that move in a smooth, gliding motion, not tumbling motility.
**Option C:** This option is incorrect as it refers to a type of motility exhibited by bacteria that move in a darting or jerking motion, not tumbling motility.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize the unique motility patterns of different bacteria, as this can aid in their identification and diagnosis. Tumbling motility, in particular, is a key feature in the identification of *C. jejuni*, which is a common cause of gastroenteritis.

**Correct Answer:** D. *Campylobacter jejuni*