Step 1: Concept
Cell organelles have specific roles. Energy production is localized to specific double-membraned structures.
Step 2: Meaning
A "powerhouse" refers to the site where the energy currency of the cell, Adenosine Triphosphate (ATP), is generated.
Step 3: Analysis
The nucleus stores genetic info, ribosomes synthesize proteins, and Golgi bodies package them. Mitochondria perform aerobic respiration, converting nutrients into ATP through the Krebs cycle and electron transport chain.
Step 4: Conclusion
Because mitochondria produce the energy required for cellular activities, they are universally termed the powerhouse of the cell.
Final Answer: (C)