ABD
E is not an answer as you cannot implement data model using custom fields. Also when we model data, we should check if we can use any out-of-box salesforce objects etc.

A B D

E should not be answer - The legacy database is relational, it needs objects, fields alone are not enough.

A - an audit of which data needs to be kept (persisted) should be done so that only relevant data is retained.
B - A relational database needs objects to build upon.
D - The legacy application owner would have the best insights about the legacy system and would be able to determine data to keep or leaave behind.

A. Identify data elements to be persisted in Salesforce. This is critical as it involves understanding which pieces of data are essential for the business processes that will be supported by Salesforce. It helps in determining what needs to be migrated and how it will be used within the Salesforce environment.

B. Map legacy data to Salesforce objects. This involves understanding how the existing data structures can be translated into Salesforce's standard and custom objects. Mapping is essential to ensure that data retains its meaning and relationships within the new environment, facilitating seamless integration and utilization.

C. Map legacy data to Salesforce custom objects. In many cases, the standard objects provided by Salesforce may not perfectly align with the data structures used in the legacy system. Custom objects allow for the creation of tailored structures that can accommodate unique data and workflows from the legacy system, ensuring a fit-for-purpose solution in Salesforce.

D and E are also important actions; however, they can be seen as components of the broader tasks defined in A, B, and C....