John Snow's germ theory work led to what action that stopped the outbreak?

• A. Quarantine travelers
• B. Cutting off access to the well
• C. Vaccination campaign
• D. Sterilization of instruments

Answer: (B)

The key idea is that cholera can spread through contaminated water, not just through the air. John Snow traced the outbreak to a single water source—the Broad Street pump—and because the pump handle was removed, people no longer used that contaminated water. That interruption of the water supply stopped new infections in the area, showing how identifying and cutting off the source can halt a transmission-driven outbreak. Quarantine of travelers isn’t addressing the local source, vaccination campaigns weren’t the tool used here, and sterilization of instruments targets clinical settings rather than a community water supply.