The boiling point of water at sea level is 100 °c. at higher altitudes, the boiling point of water will be

    The boiling point of water at sea level is 100 °C. At higher altitudes, the boiling point of water will be
a) higher, because the altitude is greater.
b) lower, because temperatures are lower.
c) the same, because water always boils at 100 °C.
d) higher, because there are fewer water molecules in the air.
==> e) lower, because the atmospheric pressure is lower.

Water boils at a lower temperature on top of a mountain because there is less air pressure on the molecules.

I hope this is helpful.