For a scenario where account information is recorded at the time the case is created and does not update when the case is further processed, while also being stored in an external system and accessed by a data page, the appropriate configuration is:

D. Select copy from a data page on the page property: This configuration ensures that when the case is created, the account information is fetched from the external system via the data page and then copied to the page property on the case. This copy is static and remains unchanged regardless of any updates to the external system or the data page after the case creation. This approach meets the requirement of capturing account information at case creation that remains constant throughout the case lifecycle.

Option A, B, and C involve referencing the data page directly in various ways, which would not fulfill the requirement for the account information to remain static after the case is created, as any updates to the data page would be reflected in the case.