<strong>A developer is quite new to CloudFormation and he is trying to use CloudFormation for his new assignment which is a web service in the Sydney region only. </strong>

Answer options:

A.In order to use AMI Id, the template needs to have a “mapping” which is inside the “Resources” section so that the template understand which AMI ID to be used during stack creation. The intrinsic function “FindInMap” is needed in the template to work with “mapping”.
B.Use a parameter for the user to input the AMI ID when the stack is created. Make sure that the parameter has the type as AWS::EC2::Image::Id.
C.In the template, add a parameter section for the AMI ID. The type of the parameter should be a String. Make sure that proper limitations are added such as the maximum length, minimum length, etc.
D.In the template, add a mapping section for all possible AMI IDs in all regions so that the CloudFormation does not need to remember any AMI IDs manually. Then in the Resource section, use FN::FindInAMI to refer the correct AMI ID.

Correct Answer – B
Mapping and “FN::FindInMap” are good to use for AMI IDs however in this case, only 1 AMI ID is needed in a unique region so that mapping and FN::FindInMap are not necessary. Besides, “Mapping” does not belong to “Resources” section so that option 1 is eliminated. Another mistake for Option D is that the correct function should be “FN::FindInMap”.
The proper method is to use Parameter. Especially when the parameter is a AWS specific parameter type such as AMI ID, the AWS specific parameter type should be used. Details please refer to https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/parameters-section-structure.html#aws-specific-parameter-types. In this case, the parameter should use AWS::EC2::Image::Id as the parameter type.
Option A & D are incorrect and explained as above.
Option C is partially correct because the AWS specific parameter type should be used. In this case, it should be AWS::EC2::Image::Id. Option B is better than
C.