What can you do to prevent the creation of duplicate users as a result of...

The correct answer is C . Duplicate user creation during a grid migration is commonly tied to identity mismatch. Slack must be able to match migrating users to the correct enterprise identity, and the most important identifier in this context is the user’s email address. Ensuring that users’ Slack email addresses match their SSO identity reduces the chance that Slack treats the same person as separate accounts during migration. Option A is incorrect because promoting guests to full members does not solve identity matching and may increase access risk. Option B is wrong because requiring login with an existing email and password does not address SSO alignment and is not the best migration control. Option D is also incorrect because usernames are not the primary identity-matching control for Enterprise Grid migration. The consultant should focus on pre-migration identity hygiene: validate email addresses, align with SSO, resolve duplicate or stale accounts, and coordinate with identity administrators before migration execution.

Reference topic: Delivery and Migration — Enterprise Grid migration preparation, duplicate-user prevention, SSO alignment, identity hygiene, and user account matching.