To ensure compliance with strict regulatory requirements for storing and processing sensitive patient data in the cloud, the following measures should be implemented:​

Assured Workloads: Deploying an Assured Workloads environment in an approved region ensures that data residency requirements are met by restricting data storage and processing to specific geographic locations. Assured Workloads provide predefined controls and configurations tailored to meet regulatory compliance needs.​

Access Approval: Configuring Access Approval ensures that certain administrative actions on patient data require explicit approval from designated compliance officers. This adds a layer of control over sensitive operations, aligning with the need for explicit approvals.​

Cloud Audit Logs and Access Transparency: Enabling Cloud Audit Logs provides a detailed record of actions taken on your data, supporting the requirement for auditability. Access Transparency logs offer visibility into Google's administrative access to your content, enhancing transparency and compliance.​

Therefore, Option C is the most appropriate choice, as it comprehensively addresses data residency, administrative control, and auditability requirements.​