When an organization uses a Private sharing model (Organ11ization-Wide Defaults), users can only see records they own or records owned by their subordinates in the role hierarchy. To open up visibility to a "subset" of records for a "selected" group of staff, the consultant must use a Sharing Rule.

Implementing the Solution:

Criteria-Based Logic: Since only a subset of Service Deliveries (e.g., those related to "Mental Health" or a specific "Program") needs to be shared, the consultant should use a Criteria-Based Sharing Rule.

Definition: The rule might state: "Share Service Delivery records where Program Name EQUALS 'Youth Outreach' with the 'Program Staff' Public Group."

Access Level: The consultant defines the level of access (Read Only or Read/Write).

Public Groups: The "selected staff" should be added to a Public Group. The sharing rule then targets this group.

Why other options are incorrect:

Public Read/Write (Option B): This would expose all records to all users, violating the nonprofit's strict security requirements.

Permission Sets / Profiles (Options C & D): These grant the functional ability to use the object (CRUD), but in a Private sharing model, they do not grant access to specific records owned by others. Sharing rules are the primary tool for record-level visibility in Salesforce.