In SAP Project System (PS), it is possible to create dependencies, known as relationships, between activities that belong to different networks. This feature, often referred to as creating "external relationships," is essential for managing complex projects where different networks might represent distinct sub-projects or work packages that are interdependent. This allows for accurate overall project scheduling and critical path analysis across the entire project landscape, even when it is structured into multiple networks. The system uses the project definition of the "external" activity to identify it.

A. A network activity can only be assigned to a single Work Breakdown Structure (WBS) element. This ensures unambiguous responsibility and clear cost allocation.

B. Material components are assigned directly to network activities to plan for material requirements for the work package, not to the more granular activity elements (internal, external, costs).

D. A network must be designated as either header-account-assigned or activity-account-assigned. These are mutually exclusive settings; a network cannot be both simultaneously.

1. Correct Answer (C): SAP Help Portal, SAP S/4HANA 2021, Project System (PS) -> Structures -> Network -> Relationships -> Creating Relationships. The documentation states, "You can also create relationships to activities in other networks."

2. Incorrect Option (A): SAP Help Portal, SAP S/4HANA 2021, Project System (PS) -> Structures -> Network -> Activity -> Assigning Activities and Activity Elements. This section details that in an activity-assigned network, "you assign the individual activities to different WBS elements." This implies a one-to-one relationship for assignment.

3. Incorrect Option (B): SAP Help Portal, SAP S/4HANA 2021, Project System (PS) -> Logistics -> Material -> Assigning Material Components. The documentation specifies, "You can assign material components that are required to carry out an activity to that activity." It does not mention assignment to activity elements.

4. Incorrect Option (D): SAP Help Portal, SAP S/4HANA 2021, Project System (PS) -> Structures -> Network -> Creating Networks. The documentation on network parameters explains the "Acct. assgt cat." (Account assignment category) field, where the user must choose between header or activity assignment, establishing them as distinct and exclusive options.