Option C is correct because the issue occurs when an HCP joins a Remote Engagement call through an Experience Cloud site link. In this flow, the external HCP typically accesses the site as the Site Guest User, so the guest user needs the correct permission set to use the remote engagement experience. Salesforce Help for creating an Experience Cloud site for Remote Engagement states that admins must assign permission sets to the guest user of the site, including Access Remote Engagement for Digital Experience. This directly matches the error in the question: the HCP reaches the site, but receives an insufficient permissions error.

Option A is incorrect because the Life Sciences Commercial Admin permission set is intended for administrative users, not the Site Guest User serving an unauthenticated Remote Engagement portal. Assigning broad admin permissions to a guest user would also be inappropriate from a security and compliance perspective. Option B is also incorrect because the requirement is not to license the HCP as a Customer Community Plus user. The scenario describes an HCP joining from a link, and the Salesforce setup guidance specifically identifies a permission-set assignment for the Site Guest User.

Therefore, the consultant should assign the Access Remote Engagement for Digital Experience permission set to the Experience Cloud Site Guest User.

=========