Multiple choice general knowledge science & technology Water boils at a lower temperature on the hills because It is cold on the hills There is less carbon dioxide on the hills There is a decrease in air pressure on the hills there is less oxygen Reveal answer Fill a bubble to check yourself C Correct answer Explanation At higher altitudes (hills), atmospheric pressure is lower than at sea level. Lower pressure reduces the boiling point of water - typically about 1°C drop for every 285 meters of elevation. This is why water boils below 100°C on mountains.