## **Core Concept**
The question tests knowledge of selective media used in microbiology for the isolation of specific bacteria, in this case, *Vibrio* species. Selective media are agar plates that inhibit the growth of certain types of bacteria while allowing others to grow. *Vibrio* species, such as *Vibrio cholerae*, are commonly isolated from stool samples.

## **Why the Correct Answer is Right**
TCBS (Thiosulfate-citrate-bile salts-sucrose) agar is a selective medium specifically designed for the isolation of *Vibrio* species, including *Vibrio cholerae*. This medium inhibits the growth of most other gram-negative and gram-positive bacteria due to its components:
- **Thiosulfate** acts as an alternate source of sulfur.
- **Citrate** inhibits the growth of many bacteria.
- **Bile salts** inhibit the growth of many gram-positive bacteria and some gram-negative bacteria.
- **Sucrose** serves as a source of carbon.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Chocolate agar is a non-selective, enriched medium used for the growth of *Haemophilus* and *Neisseria* species. It does not selectively inhibit the growth of bacteria to favor *Vibrio* species.
- **Option B:** MacConkey agar is a selective and differential medium for gram-negative bacteria, particularly for the differentiation of *Lactose fermenters* (like *E. coli*) from *non-lactose fermenters*. It does not selectively favor the growth of *Vibrio*.
- **Option D:** Blood agar is a non-selective, enriched medium that supports the growth of a wide range of bacteria. It does not inhibit the growth of bacteria and thus is not selective for *Vibrio*.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that TCBS agar is not only selective but also differential; *Vibrio cholerae* colonies appear as yellow, sucrose-fermenting colonies on this medium, while other *Vibrio* species may appear differently. This characteristic can aid in the presumptive identification of *Vibrio* species.

## **Correct Answer:** C. TCBS agar.