To facilitate electronic requests for care services from a provider to a payer system, the consultant should recommend APIs that map to standard healthcare business processes.

1. Benefit Verification (D): This API is used to request information from the payer to confirm a patient's eligibility and coverage for specific services, which is a foundational step in requesting care.

2. Referral Request (C): This API allows a provider to submit a request for a patient to receive care from another provider (e.g., a specialist), which often requires payer involvement and approval.

3. Prior Authorization (B): This API is used to formally request approval from the payer for specific medical services, procedures, or medications before they are administered to ensure they will be covered.

These three APIs directly support the workflow of requesting and authorizing care services with a payer organization.

A. Care Services: This is a general term, not a specific business-level API in Health Cloud for payer integration. The other options represent specific types of care service requests.

E. Admission, Discharge, and Transfer (ADT): This API is used to send notifications about a patient's status (e.g., hospital admission), not to request a care service from a payer.

1. Salesforce Health Cloud Developer Guide: The "Health Cloud Business APIs" section details the pre-built APIs for common healthcare processes. It explicitly lists and describes the purpose of the Benefit Verification, Prior Authorization, and Referral Request APIs for provider-payer communication.

Reference: Salesforce Help, Health Cloud Developer Guide, "Health Cloud Business APIs". This section outlines the APIs designed to "streamline communication between providers and payers," including those for verifying benefits and submitting authorization or referral requests.

2. Salesforce Health Cloud for Payers Documentation: This documentation describes how payers use Health Cloud to manage member services, including processing incoming requests from providers.

Reference: Salesforce Help, "Health Cloud for Payers", section on "Utilization Management". This area details the workflows for handling prior authorizations, benefit verifications, and referrals, which are initiated via the corresponding business APIs.