Comprehensive and Detailed In-Depth Explanation:
Process-oriented storage control (POSC) in SAP EWM manages complex processes with internal and external steps (e.g., deconsolidation, VAS). Option B ("External process step to a storage process") is correct because external steps (e.g., quality check) are assigned to a storage process in SPRO: SCM Extended Warehouse Management > Cross-Process Settings > Process-Oriented Storage Control > Define Storage Process, linking them to the overall flow. Options A, C, and D are incorrect as they don't align with POSC configuration logic.