## Core Concept
Ewing's postulates are a set of criteria used to establish a causal relationship between a microorganism and a disease. These postulates are an extension of Koch's postulates and are specifically applied to situations where Koch's postulates cannot be fulfilled, such as in cases of viral infections or diseases caused by prions.

## Why the Correct Answer is Right
Ewing's postulates are relevant in the context of molecular and genetic relationships between pathogens and diseases. They emphasize the role of specific virulence factors, genetic markers, and molecular mechanisms in disease causation. By considering the genetic and molecular aspects, Ewing's postulates provide a more comprehensive understanding of the pathogenesis of diseases.

## Why Each Wrong Option is Incorrect
* **Option A:** This option is incorrect because it does not accurately reflect the content of Ewing's postulates.
* **Option B:** This option is incorrect as it does not relate to Ewing's postulates.
* **Option C:** This option is incorrect because it does not specifically address Ewing's postulates.

## Clinical Pearl / High-Yield Fact
A key point to remember is that Ewing's postulates are used to establish a causal relationship between a microorganism and a disease, particularly in scenarios where traditional Koch's postulates are not applicable. Understanding these postulates can help in identifying the pathogenic mechanisms of various diseases.

## Correct Answer: D. Ewing's postulates.