CloudWatch Synthetics canaries require connectivity to both CloudWatch and Amazon S3 to function correctly. In a private VPC without internet access, AWS service access must be provided through VPC endpoints.

The canary needs to send metrics, logs, and execution data to CloudWatch, which requires an interface VPC endpoint for CloudWatch. It also needs to store artifacts such as screenshots and HAR files in Amazon S3, which requires a gateway VPC endpoint for S3. Without these endpoints, the canary cannot communicate with required AWS services and will fail to start.

DNS resolution and DNS hostnames must be enabled so the canary can resolve AWS service endpoints to the private IP addresses exposed by the VPC endpoints. This is a mandatory prerequisite for PrivateLink-based service access.

Option B and C incorrectly disable DNS functionality, which breaks service endpoint resolution. Option A includes invalid or irrelevant permissions and does not address private connectivity requirements.

Therefore, enabling DNS support and creating both the CloudWatch interface endpoint and the S3 gateway endpoint is the correct and complete solution.