A CloudFormation template must include an existing Amazon RDS hostname that is stored as a plaintext parameter in AWS Systems Manager Parameter Store. How should the developer reference that Parameter Store value inside the CloudFormation template?

The correct way to reference a plaintext parameter from AWS Systems Manager Parameter Store within a CloudFormation template is by using the ssm dynamic reference. This allows CloudFormation to retrieve the parameter's value during stack creation or updates. The Ref intrinsic function is used to reference resources within the same CloudFormation template or to get the value of a parameter defined within the template itself, not external Parameter Store values. The Fn::ImportValue intrinsic function is used to import values exported from other CloudFormation stacks, not directly from Parameter Store. The ssm-secure dynamic reference is used for retrieving SecureString parameters from Parameter Store, which are encrypted. Since the question specifies a plaintext parameter, ssm is the appropriate choice.