Final answer:
As altitude increases, the boiling point decreases.
Step-by-step explanation:
The boiling point is the temperature at which the vapor pressure of a liquid is equal to the external pressure. As the altitude increases, the boiling point decreases. At higher altitudes, the atmospheric pressure is lower, resulting in a lower boiling point. For example, water boils at 100°C at sea level, but at higher altitudes, such as in Denver, Colorado, it boils at about 95°C due to the lower atmospheric pressure.