Water boils at a lower temperature at high altitudes because of option 1: the air pressure is less.

When water boils, it undergoes a phase change from liquid to gas. This process requires the water molecules to gain enough energy to overcome the intermolecular forces holding them together. In simpler terms, water boils when its vapor pressure becomes equal to the atmospheric pressure.

At higher altitudes, the atmospheric pressure decreases because there is less air pushing down on the water surface. The decrease in pressure means that the water molecules do not need to gain as much energy to reach the boiling point. Therefore, water boils at a lower temperature at high altitudes compared to sea level.

Option 2, which suggests that the outside temperature is less, is not the primary reason for lower boiling temperatures at high altitudes. Although lower temperatures can contribute to a decrease in the boiling point, this effect is less significant compared to the decrease in air pressure.

Option 3, suggesting that latent heat is less, is not accurate. Latent heat refers to the amount of heat energy required to change the phase of a substance without changing its temperature. It is not directly related to the boiling point of water.

Finally, option 4, None of the above, is incorrect as the