**Core Concept**
Diphtheria toxin is a potent exotoxin produced by the bacterium Corynebacterium diphtheriae. It causes tissue necrosis and death by inhibiting protein synthesis in host cells.

**Why the Correct Answer is Right**
The toxin works by catalyzing the transfer of an ADP-ribose moiety from NAD+ to elongation factor 2 (EF-2), a critical protein involved in protein synthesis. This modification inactivates EF-2, leading to a halt in protein synthesis and eventually cell death. The toxin also has a unique mechanism of resistance, where it can be neutralized by a specific antibody, antitoxin.

**Why Each Wrong Option is Incorrect**
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**Option B:** This option is not provided, please provide the correct options.
**Option C:** This option is not provided, please provide the correct options.
**Option D:** This option is not provided, please provide the correct options.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that diphtheria toxin can be neutralized by a specific antitoxin, which is a critical component of diphtheria treatment. This antitoxin can be administered alongside antibiotics to treat the infection.

**Correct Answer:**
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