## **Core Concept**
Corynebacterium diphtheriae is a type of bacteria that causes diphtheria, a serious bacterial infection. It is a Gram-positive, non-motile rod-shaped bacterium. The bacteria produce a toxin that can cause severe respiratory and cardiac complications.

## **Why the Correct Answer is Right**
The correct answer, *Corynebacterium diphtheriae*, is the scientific name for the bacterium that causes diphtheria. This bacterium is also commonly referred to by its historical or descriptive names. One such name is *Klebs-Loeffler bacillus*, named after the scientists who first identified it.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and does not provide any relevant information.
- **Option B:** This option is also blank and does not provide any relevant information.
- **Option D:** This option is blank as well and does not offer any relevant information.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that *Corynebacterium diphtheriae* produces a toxin that causes the clinical manifestations of diphtheria, including the characteristic membrane in the throat. The bacteria are also known for their ability to cause severe disease through this toxin.

## **Correct Answer:** C. Klebs-Loeffler bacillus.