The scenario describes a complex, multi-level Engineer-to-Order (ETO) or Make-to-Order (MTO) process. The standard and most robust SAP solution is to assign the sales order item to a Work Breakdown Structure (WBS) element within a project. This allows the multi-level product structure (BOM) to be mirrored in the project's hierarchy. All subsequent production and procurement activities are then directly linked to the project and, by extension, the specific customer order. This ensures that components are produced only as needed, using project-specific stock (special stock 'Q'), which directly avoids the cost of maintaining general, unassigned inventory. This method provides comprehensive control over costs, scheduling, and logistics for complex, customer-specific products.

B. Assign a network to a sales order

A network represents activities, while the WBS element is the primary integration object for cost collection, material management, and linking to the sales order.

C. Assign several production orders to a sales order

While this is a valid Make-to-Order approach, a project provides superior structuring, control, and integrated cost management for the complex, multi-level production scenario described.

D. Assign one production order to a sales order

A single production order is insufficient for a multi-level production environment, which requires separate orders for various semi-finished goods and assemblies.

1. Official Vendor Documentation: SAP Help Portal, SAP S/4HANA 2021, "Project System (PS) -> Sales and Distribution Processing in the Project System". This section details the process of assigning sales order items to WBS elements, making the WBS element the account assignment object for all related costs and revenues, which is central to the ETO scenario.

2. Official Vendor Documentation: SAP Help Portal, SAP S/4HANA 2021, "Project System (PS) -> Material -> Material Requirements Planning (MRP) -> Executing Material Requirements Planning for Projects". This document explains that running MRP for a project (Transaction MD51) generates procurement proposals (e.g., planned orders, purchase requisitions) that are specifically assigned to the WBS elements, leading to the creation of project stock.

3. Official Vendor Documentation: SAP Learning, Course TS452 "SAP S/4HANA Project System", Unit 5: "Project Structures". This official training material describes how WBS hierarchies are used to model complex undertakings, including customer-specific projects triggered by sales orders in an ETO environment, to manage scope, time, and cost.