You’re planning on using the AWS CodeDeploy tool for the deployment of your application. Which of the following is used to specify how your application will be deployed to the underlying instances?

Answer options:

A.appConfig.json
B.DeploymentGroup
C.appConfig.YAML
D.appspec.yml

Answer - D
This is mentioned in the AWS Documentation.
Because of what is mentioned in the documentation on what is the functionality of the appspec.yml file, all other options are incorrect.
Refer to page 19 and 25 of the below in
https://docs.aws.amazon.com/codedeploy/latest/userguide/codedeploy-user.pdf
For more information on Code Deploy, please refer to the below URL-
https://docs.aws.amazon.com/codedeploy/latest/userguide/welcome.html
NOTE:
As per AWS docs, AppSpec Files on an AWS Lambda Compute Platform is a YAML-formatted or JSON-formatted file used by AWS CodeDeploy to manage deployment. However, according to AWS, an application specification file (AppSpec file) is unique to the AWS CodeDeploy service. The AppSpec file is used to manage each deployment as a series of lifecycle event hooks, which are defined in the file.
According to our question options, A & C are referring to an appConfig file that is wrong.