Explanation
At implementation time, the transformation maps that are associated with the external-facing interfaces must be modified to map the extensible flexfield attributes to the enterprise business object attributes.
References:http://docs.oracle.com/cd/E25054_01/fusionapps.1111/e20386/F476421AN2E51E.htm

Explanation
C: TheAttachments Flag is a flag that indicates the presence of an attachment that can be downloaded online.
E:The Category Manager may receive inquiries from a supplier asking for clarification about a negotiation requirement or line attribute. The Category Manger pauses the negotiation while she is conducting a discussion with the supplier.
References:https://docs.oracle.com/cd/E56614_01/procurementop_gs/OAPRC/F1007481AN23290.htm#F10074
https://docs.oracle.com/en/cloud/saas/procurement/20a/oaprc/manage-supplier-negotiations.html#OAPRC12133

Explanation
How can I change the due dates, notifications, and other contract deliverable details?
You can change the due dates, notifications, and other contract deliverable definition details in the Deliverables tab of a contract that is in Draft or Under Amendment status. Once the contract becomes active and deliverables are automatically activated creating deliverable instances, you can only make changes to deliverables status, notes and attachments using the Manage Deliverables task. For internal deliverables with a fixed due date that you can manually activate at any time irrespective of contract status, you can only make changes to deliverable definition details before you activate them.
References:https://docs.oracle.com/cd/E56614_01/procurementop_gs/FASCA/F1174613AN14980.htm

Explanation
Without the site assignment model each client BU would be forced to establish its own relationship with the supplier. The service provider relationship between the client BU and procurement BU is defined in the business unit setup.
References: Oracle Procurement Cloud Using Procurement (Release 9), page 30