A cold-aisle + hot-aisle with aisle containment, compared with a fully mixed room, most directly improves (conceptual)?

Choices

• (A) Oil return to compressor in split
• (B) Tower approach only in winter
• (C) Separation and stability of hot/cold streams, better ΔT/CFM+lower fan kW, subject to code/fires
• (D) NPSH in AHU return