Final answer:
For temporary data on an Amazon EC2 instance, Amazon Elastic Block Store (EBS) should be used as it provides block-level storage volumes suitable for frequently changing data and can be automatically deleted when the instance is terminated.
Step-by-step explanation:
If a cloud engineer running an Amazon EC2 instance needs to store temporary data and won't be keeping the data long-term, they should use Amazon Elastic Block Store (EBS) as the attached storage resource. Unlike Amazon S3, which is designed for long-term storage and provides high durability for objects, Amazon EBS provides block-level storage volumes that can be attached to EC2 instances for temporary storage of data that changes frequently, such as system logs or temporary files during computation processes.
Additionally, when an EC2 instance is terminated, the temporary EBS volumes can be set to delete automatically, making EBS a more fitting choice for temporary storage needs.