Answer: a
Explanation: vaporization requires the most energy because it contains the most heat. Steam is water being vaporized, it occurs when the energy causes the molecules in the water to vibrate really fast and rub against each other, which results in heat and vaporization. Just like when you rub your hands together, the energy you’re using to create heat becomes evident when you rub them together for too long and you begin to become tired, this is because of the expending of energy in exchange for heat.