Water vapor condenses on the cold bottle surface

Steps:

• Warm air holds water vapor and contacts the cold bottle.
• The bottle's surface cools the air near it below the dew point.
• Water vapor in the air changes from gas to liquid state.
• Liquid water forms as drops on the bottle's exterior.

Why A is correct:

• Condensation occurs when water vapor cools and transitions to liquid, as defined by the phase change process at or below the dew point.

Why the others are wrong:

• B: Conduction transfers heat through direct contact but does not change water vapor to liquid.
• C: Convection moves heat via fluid currents but does not cause phase change to drops.
• D: Evaporation converts liquid to vapor, the reverse of drop formation.

Final answer: A