## Core Concept
The question tests the knowledge of bacterial morphology, specifically the shape and arrangement of bacteria. Coccobacilli are a type of bacteria that are intermediate in shape between cocci (spherical) and bacilli (rod-shaped), often appearing as short, stout rods.

## Why the Correct Answer is Right
The correct answer, *Listeria monocytogenes*, is a well-known example of a coccobacillus. This bacterium is a gram-positive, facultative anaerobe that exhibits a characteristic morphology of being a short rod or coccobacillus. This shape is significant for its identification under the microscope.

## Why Each Wrong Option is Incorrect
* **Option A:** *Staphylococcus aureus* is a gram-positive coccus, not a coccobacillus. It appears as clusters of spherical cells.
* **Option B:** *Escherichia coli* is a gram-negative bacillus, appearing as long, thin rods, not coccobacilli.
* **Option D:** *Streptococcus pneumoniae* is a gram-positive coccus, often seen in pairs or chains, not a coccobacillus.

## Clinical Pearl / High-Yield Fact
A key clinical point to remember is that *Listeria monocytogenes* is a pathogen that can cause severe infections, particularly in immunocompromised individuals, pregnant women, and neonates. Its identification as a coccobacillus can be a critical clue in the microbiological diagnosis.

## Correct Answer Line
**Correct Answer: C. Listeria monocytogenes**