Correct answer - "EBS volumes are AZ locked" : You can attach an available EBS volume to one of
your instances that is in the same Availability Zone as the volume.
Incorrect:
"EBS volumes are region locked" - Its confined to an Availability Zone and not by region
"He's missing IAM permissions" - This is a possibility as well but if permissions are not an
issue then you are still confined to an availability zone
"The EBS volume is encrypted" - This doesn't affect the ability to attach an EBS volume.