Which primary function is most directly associated with mitochondria in eukaryotic cells?

• A. They synthesize proteins for secretion by translating mRNA on bound ribosomes.
• B. They package DNA into chromosomes and control gene transcription in the nucleus.
• C. They modify and sort proteins for delivery to lysosomes or the plasma membrane.
• D. They generate most cellular ATP through oxidative phosphorylation during aerobic respiration.

Answer: (D)