As an architect, you have decided to use CloudFormation instead of OpsWorks or Elastic Beanstalk for deploying the applications in your company. There is a requirement to include a custom resource using the AWS CloudFormation. How can you achieve this?

Answer options:

A.Add a custom mapping in your template to specify which custom resource would be used.
B.Create a custom resource AWS::CloudFormation::CustomResource in the CloudFormation template.
C.Create a Lambda function resource in the CloudFormation template and use the Lambda function to interact with the custom resource.
D.Create an SNS topic resource in the CloudFormation template and subscribe to the SNS topic for the custom resource.

Answer - B
Custom resources enable you to write custom provisioning logic in templates that AWS CloudFormation runs anytime you create, update (if you changed the custom resource), or delete stacks. For example, you might want to include resources that aren`t available as AWS CloudFormation resource types. You can include those resources by using custom resources (AWS::CloudFormation::CustomResource). That way, you can still manage all your related resources in a single stack.
Options A, C and D are incorrect because they are not the correct methods to specify a custom resource in the AWS CloudFormation template.
For more information on custom resources in CloudFormation, please visit the below URL:
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/template-custom-resources.html