Polls and Out of Office are two ways that CK can use Chatter to gather feedback and understand availability. Polls allow users to create surveys and collect opinions from other users. Out of Office lets users set a status message and an end date to inform others when they are away or busy. Streams and Topics are not related to the problem.

The solution that should meet this requirement is updating the support team profile to remove the Bronze record type. This way, the support team users will not be able to create new cases with the Bronze record type, as it will not appear in their record type selection list. Option A is incorrect because updating the organization-wide defaults to private for Case does not affect the record type availability, but rather the record access level. Option C is incorrect because creating permission set group for Case that includes Platinum and Diamond record types does not prevent the support team users from creating new cases with the Bronze record type, as they may still have access to it through their profile. Option D is incorrect because making the record type hidden to support users and updating sharing roles to private does not prevent the support team users from creating new cases with the Bronze record type, as they may still have access to it through their profile.