## Core Concept
Diphtheria is an infectious disease caused by Corynebacterium diphtheriae, characterized by the production of a toxin that can lead to severe respiratory and cardiac complications. The disease primarily affects the respiratory system but can also impact the cardiovascular, nervous, and renal systems. Complications arise mainly from the toxin's local effects on the respiratory tract and its systemic effects.

## Why the Correct Answer is Right
Toxemia and myocarditis are well-recognized complications of diphtheria. Toxemia occurs due to the systemic spread of the diphtheria toxin, leading to multi-organ involvement. Myocarditis, or inflammation of the heart muscle, is a serious complication that can result from the toxin's direct effect on the heart. On the other hand, options provided need to be evaluated for their relevance to known complications of diphtheria.

## Why Each Wrong Option is Incorrect
- **Option A:** Myocarditis is indeed a complication of diphtheria, as mentioned.
- **Option B:** Toxemia is also a recognized complication.
- **Option C:** This option needs to be a known complication to assess its correctness.
- **Option D:** This is stated as the correct answer but without the specific text, we infer based on process of elimination and knowledge of diphtheria complications.

## Clinical Pearl / High-Yield Fact
A key clinical pearl is that diphtheria can lead to respiratory obstruction, which is a critical and potentially life-threatening complication. Early recognition and management of diphtheria, including administration of diphtheria antitoxin and antibiotics, are crucial to prevent these complications.

## Correct Answer: D.