Water vapor cools and condenses on the bottle's surface

Steps:

• Warm air holds water vapor; the bottle's cool surface lowers the temperature nearby.
• When air temperature drops below the dew point, water vapor changes to liquid.
• This forms visible drops on the outside of the bottle.
• The process matches the definition of phase change from gas to liquid.

Why A is correct:

• Condensation is the process where water vapor (gas) turns into liquid water upon cooling, as defined in thermodynamics.

Why the others are wrong:

• B. Conduction transfers heat through direct contact between solids, not forming liquid drops.
• C. Convection moves heat via fluid currents, like air rising, but doesn't create water droplets.
• D. Evaporation changes liquid to gas, the opposite of drops forming from vapor.

Final answer: A