This is a governance decision before it is a configuration click. In this case, The proper configuration is B.
External ID; C. Unique. Salesforce import tools differ by data volume, matching logic, and operation. Data Import Wizard is guided and duplicate-aware for supported objects; Data Loader is stronger for larger updates, upserts, and clearing values.
The stem gives enough detail to reject surface-level fixes. Salesforce should be configured so the behavior is enforced or rendered by the feature designed for it. When the requirement touches Data Modeling and Management, the builder should avoid crossing into a different layer unless there is a real platform limitation.
The selected answer follows that discipline and creates the least surprising result for admins and users.
The rejected choices solve different problems. A (Text (encrypted)) is less defensible because That field type either stores the wrong kind of value or fails to support the required behavior as cleanly as the selected option.
D (Request) does not fit cleanly; it solves a symptom of the problem rather than the Salesforce mechanism that owns the result. The configuration remains understandable for future admins because the decision is visible in metadata rather than buried in a workaround.
For imports, the builder should choose the tool based on record count, supported object, operation type, duplicate handling, and the presence of an external identifier.
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