**Core Concept**
Cholera, caused by Vibrio cholerae, is a highly infectious diarrheal disease that requires effective disinfection of contaminated stool to prevent its spread. The best disinfectant for cholera stool is a substance that can inactivate or kill the bacteria, thereby preventing the transmission of the disease.

**Why the Correct Answer is Right**
The correct answer is **Bleach**. Bleach is a strong disinfectant that contains sodium hypochlorite, which is effective against a wide range of microorganisms, including Vibrio cholerae. When used at a concentration of 1:100 (1 part bleach to 100 parts water), bleach can inactivate cholera bacteria on surfaces and in stool. The sodium hypochlorite in bleach works by disrupting the cell membrane of the bacteria, ultimately leading to cell death.

**Why Each Wrong Option is Incorrect**
**Option A:** **Formaldehyde** is a potent disinfectant, but it is not the best choice for disinfecting cholera stool because it is highly toxic and requires specialized handling. Additionally, formaldehyde is not as effective as bleach against Vibrio cholerae.

**Option C:** **Quaternary ammonium compounds** (quats) are commonly used as disinfectants, but they are not effective against Vibrio cholerae. Quats work by disrupting the cell membrane of bacteria, but they are not as potent as bleach against this particular organism.

**Clinical Pearl / High-Yield Fact**
When using bleach as a disinfectant, it is essential to mix it with water at a ratio of 1:100 and let it sit for 10-15 minutes before rinsing to ensure effective inactivation of cholera bacteria.

**Correct Answer: B. Bleach**