Correct answer - "!GetAtt" : The Fn::GetAtt intrinsic function returns
the value of an attribute from a resource in the template. We can use the above function to get
the regions ID attribute of the required EC2 instance by passing region ID as the attributeName
and EC2 instance ID as logicalNameOfResource.
Incorrect:
!Ref - Returns the value of the specified parameter or resource
!Sub - Substitutes variables in an input string with values that you specify
!FindInMap - For example you can use this in the Mappings section that contains a
single map, RegionMap, that associates AMIs with AWS regions