Intrinsic Functions

Correct Answer: Fn::GetAZs

To get the current region of your stack using Intrinsic Functions, you should use Fn::GetAZs. The Fn::GetAZs function returns an array that lists the Availability Zones for a specified region. If you don't specify a region, AWS CloudFormation uses the region of the stack as the default value. Here's an example of how you can use Fn::GetAZs in your CloudFormation template: AWSTemplateFormatVersion: '2010-09-09' Description: Example template using Fn::GetAZs Resources: MySubnet: Type: AWS::EC2::Subnet Properties: VpcId: !Ref MyVPC CidrBlock: 10.0.0.0/24 AvailabilityZone: !Select [ 0, !GetAZs '' ] In this example, the Fn::GetAZs function is used without specifying a region, so it defaults to the region of the stack. The Fn::Select function is then used to select the first Availability Zone from the array returned by Fn::GetAZs. Note that the other Intrinsic Functions mentioned in the options serve different purposes: - Fn::GetAtt retrieves the value of an attribute from a resource in the template. - Fn::Join appends a set of values into a single value, separated by a specified delimiter. - Fn::Sub substitutes variables in an input string with values that you specify. - Fn::ImportValue returns the value of an output exported by another stack. - Fn::Select returns a single object from a list of objects by index. Therefore, to get the current region of your stack using Intrinsic Functions, you should use Fn::GetAZs.

Correct Answer: Fn::Select

Fn::Select returns a single element from a list by index, which is exactly what you need when you must pick a specific instance ID from a list to associate an Elastic IP. Fn::If only chooses between two values based on a condition, Fn::GetAtt retrieves an attribute from a named resource (not an indexed list element), and Fn::Equals simply compares two values and returns true/false.

Correct Answer: Fn::Join

To create an EC2 instance with a name tag value as a combination of the stack name and a user-provided string, you can use the Fn::Join function like this: {"Fn::Join": ["", [{"Ref": "AWS::StackName"}, {"Ref": "UserString"}]]}. This combines both values without any delimiter. The other Intrinsic functions mentioned are not suitable for merging string values.