A company uses Amazon EC2 instances to host a website.

The most secure and AWS-recommended way for EC2 instances to access AWS services is by using IAM roles attached through instance profiles. Option C correctly implements this pattern.

IAM roles provide temporary credentials via the EC2 metadata service, eliminating the need for long-term access keys. Using CloudFormation ensures consistent, repeatable deployments across Regions while maintaining security best practices.

All other options expose long-term credentials, increasing the risk of compromise and violating AWS security guidance. Therefore, C is the correct and most secure solution.