Droplets in disease transmission are characterized by which of the following?

• A. Size greater than 100 micrometers; settling velocity greater than 1 foot/second; suspension time less than 3 seconds; flight range 1-2 meters
• B. Size 2-10 micrometers; suspension time hours; flight range 0.5 meters
• C. Size 0.1-1 micrometer; suspend for days
• D. Size 10-100 micrometers; settling velocity 0.01 ft/sec; flight range 5-10 meters

Answer: (A)

Droplets are large particles whose behavior is dominated by gravity: they form when someone coughs or sneezes and quickly settle out of the air. Because they are typically bigger than about 100 micrometers and have a fast settling rate, they don’t stay airborne long—often only a few seconds—and don’t travel far, usually around 1–2 meters. That combination of size, rapid settling, brief suspension, and short travel distance is the best fit for the description of droplets. The other choices describe much smaller particles that can remain suspended for hours or days and travel farther, which aligns with aerosols rather than droplets.