At a hill station, the boiling point of water will be _____.

The correct answer is Option (3) → Less than that at sea level

Water boils when its vapour pressure becomes equal to the air pressure above it. On a hill station the air is thinner and the atmospheric pressure is lower, so the water reaches that pressure at a lower temperature and boils below 100°C (at sea level it boils at 100°C). This is why food takes longer to cook in the hills and a pressure cooker is used there.