**Core Concept**
The ideal dose of Diphtheria antitoxin is crucial for effective treatment of Diphtheria, a bacterial infection caused by Corynebacterium diphtheriae. Diphtheria antitoxin is a neutralizing antibody that targets the diphtheria toxin, preventing its harmful effects on the body.

**Why the Correct Answer is Right**
The correct dose of Diphtheria antitoxin is 20,000-40,000 units, administered intravenously or intramuscularly. This dose is sufficient to neutralize the toxin and prevent further tissue damage. The antitoxin works by binding to the diphtheria toxin, preventing it from binding to and damaging the host cells. The toxin is then neutralized and excreted from the body.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the dose of Diphtheria antitoxin is not specified. The correct dose is crucial for effective treatment.
* **Option B:** This option is incorrect because the dose of 10,000 units is too low to effectively neutralize the diphtheria toxin.
* **Option C:** This option is incorrect because the dose of 100,000 units is too high and may cause adverse reactions.

**Clinical Pearl / High-Yield Fact**
It is essential to administer Diphtheria antitoxin promptly, ideally within 2-4 days of symptom onset, to prevent serious complications and mortality. Delayed treatment can lead to severe consequences, including cardiac and neurological damage.

**Correct Answer: D. 100,000 units**