Why do muscle cells typically contain a high number of mitochondria compared with many other cell types?

• A. They require mitochondria mainly to store calcium long-term as an inert mineral deposit.
• B. They have a high demand for ATP to power repeated contraction, and mitochondria generate ATP primarily through oxidative phosphorylation.
• C. They contain many mitochondria because mitochondria are the primary site of DNA replication in muscle cells.
• D. They need many mitochondria to synthesize and secrete large amounts of extracellular matrix proteins.

Answer: (B)