The pressure of earth's atmosphere decreases with altitude, or height above sea level. as a result, the boiling point of water is on tall mountain peaks.

As a result, the boiling point of water is lower on tall mountain peaks.
For example, on top of Mount Everest, at 8,848 m (29029 ft) elevation, the pressure is about 34 kPa (255 Torr) and the boiling point of water is 71°C (160 °F).
The boiling point of a substance is the temperature at which the vapor pressure of the liquid equals the pressure surrounding the liquid and the liquid changes into a vapor.

The answer would be  b. hope this !

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