Which two methods should an architect use to trace back configuration changes to the detailed requirements?

As part of a phased Salesforce rollout. there will be 3 deployments spread out over the year. The requirements have been carefully documented.

Which two methods should an architect use to trace back configuration changes to the detailed requirements? Choose 2 answers
A . Review the setup audit trail for configuration changes.
B . Put the business purpose in the Description of each field.
C . Maintain a data dictionary with the justification for each field.
D . Use the Force.com IDE to save the metadata files in source control.

Answer: B,C