What is the correct reason for water droplets forming outside a cold bottle?

Correct answer: Moist outside air cools and condenses on the bottle surface

Correct answer: A. The droplets come from the air outside, not from water passing through the glass. Air contains some water vapour. When this moist air touches the cold bottle, it loses heat and its temperature may fall to the dew point. At or below the dew point, the air cannot retain all its vapour, so the vapour changes into tiny liquid-water droplets on the bottle surface. This change from gas to liquid is called condensation. A is correct because it gives both the source, outside moist air, and the process, cooling followed by condensation. B is wrong because ordinary glass is not a porous path for the water inside. C is wrong because oxygen does not become water merely by touching a cold bottle. D is wrong because cooling does not make air completely dry; it can actually cause vapour to condense. Memory cue: cold surface plus moist air equals condensation.