Which solution will meet these requirements?

Explanations:

Creating an IAM user with access keys and secret keys requires managing those credentials, which contradicts the requirement to make secure API requests without managing security credentials. This option does not follow the principle of least privilege as it grants broads3:*permissions.

Associating the EC2 instance with an IAM role that has a policy allowings3:ListBucketands3:*Objectpermissions for specific S3 buckets allows secure API requests without managing credentials. This approach follows the principle of least privilege by granting only the necessary permissions for the specified buckets.

Associating the EC2 instance with an IAM role that has theAmazonS3FullAccessmanaged policy grants excessive permissions (full access to all S3 resources), which violates the principle of least privilege. The developer should limit access to only the required S3 buckets and actions.

Creating a bucket policy to allows3:ListBucketands3:*Objectpermissions to the EC2 instance does not eliminate the need for managing security credentials. While it can restrict access, it does not provide a secure way to authenticate without using IAM roles associated with the instance.