**Core Concept**
Corynebacterium diphtheriae is a Gram-positive, rod-shaped bacterium that causes diphtheria, a serious infectious disease characterized by a toxin-mediated respiratory tract infection. The bacterium produces diphtheria toxin, which is responsible for the disease's pathogenesis.

**Why the Correct Answer is Right**
Diphtheria toxin is a potent exotoxin that inhibits protein synthesis by cleaving the elongation factor 2 (EF-2) of the host cell, leading to cell death. The toxin is produced by the bacterium in response to the presence of iron and is encoded by the tox gene. The toxin is secreted by the bacterium and causes local tissue damage and systemic complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not provided.
* **Option B:** Incorrect, as Corynebacterium diphtheriae is not a Gram-negative bacterium.
* **Option C:** Incorrect, as Corynebacterium diphtheriae does not produce tetanus toxin.
* **Option D:** Incorrect, as Corynebacterium diphtheriae does not cause tuberculosis.

**Clinical Pearl / High-Yield Fact**
Corynebacterium diphtheriae can be differentiated from other Gram-positive rods by its metachromatic granules, which are visible under a microscope after staining with Albert's stain. This characteristic is a key diagnostic feature of the bacterium.

**Correct Answer: Not Provided. Please provide options to complete the explanation.**