More energy is spent in climbing stairs, because

More energy is spent in climbing stairs because the person works against gravity; option [A]. When climbing stairs, the individual exerts force in the opposite direction to gravity’s pull, lifting their body against it. This requires energy expenditure, as work is done to overcome gravity’s resistance. In contrast, on flat ground, the person’s horizontal movement doesn’t involve significant gravitational opposition. The gravitational force acts perpendicular to the motion, so no work is done against it, unlike when ascending stairs where gravity opposes vertical motion. Therefore, option A, “the person works against gravity,” accurately explains the increased energy expenditure in stair climbing. This phenomenon aligns with the principle of conservation of energy, where the energy spent in lifting the body against gravity is transformed into potential energy. Consequently, climbing stairs demands more energy compared to walking on level ground due to the additional work required to overcome gravity’s resistance, highlighting the interplay between gravitational forces and human movement in energy expenditure.