**Core Concept**
Transport of stool samples in suspected cases of shigellosis requires a medium that maintains the viability of the bacteria while preventing overgrowth of other microorganisms. Buffered glycerol saline is a suitable choice for this purpose due to its ability to preserve the bacteria and inhibit the growth of contaminants.

**Why the Correct Answer is Right**
Buffered glycerol saline is a transport medium that maintains a stable pH and provides a hypotonic environment, which is ideal for preserving the viability of shigella bacteria. This medium contains a buffer system to maintain the pH, preventing the growth of other bacteria that may be present in the stool sample. Additionally, the low osmolarity of the medium helps to prevent the lysis of shigella cells, ensuring that they remain intact and viable for further analysis. The presence of glycerol in the medium also helps to prevent the growth of other microorganisms, making it an ideal choice for transporting stool samples in suspected cases of shigellosis.

**Why Each Wrong Option is Incorrect**
**Option A:** Deoxycholate medium is a selective medium used for the isolation of Gram-negative bacteria, but it is not suitable for the transport of stool samples as it can inhibit the growth of shigella bacteria.

**Option B:** Blood agar is a general-purpose medium used for the cultivation of a wide range of bacteria, but it is not ideal for the transport of stool samples as it can support the growth of other microorganisms, potentially overgrowing the shigella bacteria.

**Option C:** Nutrient broth is a general-purpose medium used for the cultivation of bacteria, but it is not suitable for the transport of stool samples as it can support the growth of other microorganisms and does not provide the necessary conditions to preserve the viability of shigella bacteria.

**Clinical Pearl / High-Yield Fact**
When transporting stool samples in suspected cases of shigellosis, it is essential to use a transport medium that maintains the viability of the bacteria while preventing overgrowth of other microorganisms. Buffered glycerol saline is a suitable choice for this purpose, and its use can help to ensure accurate diagnosis and treatment.

**✓ Correct Answer: D. Buffered glycerol saline**