Correct answer - "S3": If you upload a local template file, AWS CloudFormation uploads it to an Amazon Simple Storage Service (Amazon S3) bucket in your AWS account. If you don't already have an S3 bucket that was created by AWS CloudFormation, it creates a unique bucket for each region in which you upload a template file. If you already have an S3 bucket that was created by AWS CloudFormation in your AWS account, AWS CloudFormation adds the template to that bucket.
Incorrect:
"EBS" - Amazon EBS is a recommended storage option when data must be quickly accessible and requires long-term persistence
"EFS" - EFS is a file storage service where you mount the file system on an Amazon EC2 Linux-based instance which is not an option for CloudFormation
"ECR" - Amazon ECR eliminates the need to operate your container repositories or worry about scaling the underlying infrastructure which does not apply to CloudFormation
For more information visit https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/cfn-using-console-create-stack-template.html
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