Answer:
b.
At higher elevations, it would take longer to hard boil an egg, because there is a lower boiling point, so the egg is boiling in water at a lower temperature.
Step-by-step explanation:
According to the question, the lower atmospheric pressure at higher elevations lower down the boiling point of the water. This means that water boils at lower temperatures at the higher elevations.
To hard boil an egg, one needs to boil is longer at higher altitudes. This is because the lower boiling point of water makes it boil at a lower temperature which in turn would provide lesser heat energy to egg to boil. To compensate it, the egg should be boiled for longer.