As part of a phased Salesforce rollout.

Option B is correct because putting the business purpose in the Description of each field is a method that an architect can use to trace back configuration changes to the detailed requirements1. The Description of each field provides a brief explanation of what the field is used for and why it is needed2. Option D is correct because using the Force.com IDE to save the metadata files in source control is another method that an architect can use to trace back configuration changes to the detailed requirements1. The Force.com IDE is an integrated development environment that allows developers to work with Salesforce metadata files and Apex code3. Source control is a system that tracks and manages changes to code and configuration files4. Option A is not correct because reviewing the setup audit trail for configuration changes is not a method to trace back configuration changes to the detailed requirements, but a way to monitor and audit the changes made in the setup area. Option C is not correct because maintaining a data dictionary with the justification for each field is not a method to trace back configuration changes to the detailed requirements, but a document that provides information about the data entities and attributes in a system.