Final answer:
Muscle cells require large amounts of energy and therefore contain a large number of mitochondria, the cell's powerhouse for ATP production necessary for muscle contraction.
Step-by-step explanation:
Because muscle cells require large amounts of energy to produce movement, one would expect muscle cells to contain a large number of mitochondria. Mitochondria are often referred to as the "powerhouses" or "energy factories" of a cell because they are responsible for producing adenosine triphosphate (ATP), which is the cell's main energy-carrying molecule. The process of creating ATP from the breakdown of glucose is known as cellular respiration, a critical process for muscle contraction and other energy-demanding cellular activities.
Specifically, active muscle cells, like those of a marathon runner, contain very high concentrations of mitochondria to meet the high energy demands of continuous muscle contraction. This also applies to other cells with high energy requirements, such as sperm cells. Therefore, the correct answer to the question is C) Mitochondria.