The correct answer is B. During a grid migration, users should be prepared for disruption because the migrating workspace becomes unavailable and users are signed out while the migration process completes. This is exactly the kind of operational impact that must be communicated in advance so users do not assume Slack is broken or raise unnecessary support tickets. Option A is incorrect because it understates the migration impact and would create poor launch communication. Option C is also incorrect because the workspace is not partially usable for direct messages while channels are unavailable; the migration affects access to the workspace. Option D is wrong because users are not ''deactivated at the org level'' as the normal communication point. The consultant should ensure the migration communication plan includes timing, expected downtime, user sign-out behavior, post-migration login instructions, support contacts, and where users should go if they experience access issues after completion. Clear pre-migration communication reduces confusion and protects user trust during the transition.