**Core Concept**
The transport of stool specimens is crucial for maintaining the viability of organisms, especially in the diagnosis of infectious diseases. This requires a medium that preserves the specimen during transport to the laboratory.

**Why the Correct Answer is Right**
Since the correct answer is not provided, I will explain the general principle. Stool specimens are typically transported in a **Cary-Blair medium**, which is a non-nutritive medium that maintains the viability of organisms without allowing overgrowth of commensals.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because it is not a standard transport medium for stool specimens.
**Option B:** Similarly, this option is not typically used for transporting stool.
**Option D:** This is also incorrect as it does not preserve the organisms as required.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that the choice of transport medium depends on the suspected pathogens, and **Cary-Blair medium** is commonly used for stool specimens to preserve enteric pathogens.

**Correct Answer:** D. Cary-Blair medium.