The conclusion that can be drawn from the information that muscle cells have more mitochondria than skin cells is:
D. Muscle cells use more energy than skin cells.
Mitochondria are often referred to as the "powerhouses" of the cell because they are responsible for producing energy in the form of ATP through cellular respiration. Since muscle cells require more energy for contraction and movement, it is logical that they have a higher number of mitochondria compared to skin cells, which have lower energy demands.