## Core Concept
The DPT (diphtheria, pertussis, and tetanus) vaccine is a combination vaccine used to protect against diphtheria, pertussis, and tetanus. Diphtheria toxoid is a key component, which is produced by inactivating the toxin produced by Corynebacterium diphtheriae. The potency of diphtheria toxoid is measured in Loeffler units.

## Why the Correct Answer is Right
The correct dose of diphtheria toxoid incorporated in the DPT vaccine per dose is . This dose is considered sufficient to induce immunity against diphtheria without causing significant adverse reactions. The measurement in Loeffler units ensures standardization of the toxoid's potency.

## Why Each Wrong Option is Incorrect
* **Option A:** - This dose seems too low for effective immunization against diphtheria.
* **Option B:** - This is not the standard dose used in DPT vaccines.
* **Option D:** - This dose appears too high and might increase the risk of adverse reactions without providing a significantly better immune response.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the potency of vaccines, including the diphtheria toxoid in DPT vaccines, is crucial for their effectiveness and safety. The standard dose of in Loeffler units is specifically chosen to balance efficacy and safety.

## Correct Answer: C.