Breathing on a cold surface such as a piece of glass causes water droplets to appear on the surface. This proves the presence of:

Explanation

Option A: Carbon dioxide (CO2) is a gas that is naturally present in the Earth's atmosphere. It is a greenhouse gas and contributes to global warming. We exhale CO2 when we breathe out, and it is also released into the atmosphere through the burning of fossil fuels. However, CO2 is not directly responsible for water droplets appearing on a cold surface.Option B: When we exhale, the air contains water vapor from the moisture in our lungs and respiratory system. This warm, moist air can cause water droplets to form on a cold surface when it comes into contact with it. This is because the temperature of the air drops, causing the water vapor to condense into tiny droplets on the surface. Option C: Oxygen (O2) is a gas that is necessary for us to breathe and survive. It makes up about 21% of the Earth's atmosphere. However, like CO2, it is not directly responsible for water droplets appearing on a cold surface.Option D: This option is not correct because while CO2 and O2 are present in the air, they are not directly responsible for the water droplets appearing on a cold surface. Only moisture in expired air is directly responsible for this phenomenon.