## **Core Concept**
The question tests knowledge of the characteristics of *Clostridium* species, specifically their motility. *Clostridium* is a genus of Gram-positive, anaerobic, spore-forming bacteria. Their motility, or lack thereof, is an important distinguishing feature among species.

## **Why the Correct Answer is Right**
*Clostridium perfringens* is known for being non-motile. This characteristic is crucial for its identification. It is a common cause of food poisoning and gas gangrene. The lack of motility in *C. perfringens* distinguishes it from other *Clostridium* species that are motile, such as *Clostridium difficile*, which is known for its role in antibiotic-associated diarrhea and colitis.

## **Why Each Wrong Option is Incorrect**
* **Option A:** While certain *Clostridium* species are motile, without specifying, it's hard to directly refute. However, many *Clostridium* species are indeed motile, which would not match the description of non-motile.
* **Option B:** Similarly, without a specific species, it's challenging to directly address. However, the question seeks a non-motile species, implying that if B is a motile species, it would be incorrect.
* **Option C:** This option is not directly addressed but given that *C. perfringens* is the correct answer, any motile *Clostridium* species would be incorrect.
* **Option D:** This option is also not directly addressed but would be incorrect for the same reason as option C, assuming it represents a motile species.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that *Clostridium perfringens* is a leading cause of gas gangrene and food poisoning. It is identified by its non-motility, large, gram-positive rods, and the production of many toxins, most notably the alpha-toxin (a phospholipase C). Rapid identification and treatment are crucial due to the severe nature of the diseases it causes.

## **Correct Answer:** C. Clostridium perfringens