Which statement correctly contrasts commissioning and retro-commissioning?

Which statement correctly contrasts commissioning and retro-commissioning?

• A. Commissioning verifies systems meet design in new buildings; retro-commissioning re-tunes existing systems to improve performance.
• B. Commissioning is only for energy efficiency in existing buildings; retro-commissioning is for new construction.
• C. Commissioning and retro-commissioning mean the same thing.
• D. Commissioning only tests structural integrity.

Answer: (A)