If I want CloudFormation stack status updates to show up in a continuous delivery system as close to real-time as possible, how should I achieve this?

Answer options:

A.Use a long poll on the Resources object in your CloudFormation stack and display those state changes in the UI for the system.
B.Use a long-poll on the ListStacksAPI call for your CloudFormation stack and display those state changes in the UI for the system.
C.Subscribe your continuous delivery system to an SNS topic that you also tell your CloudFormation stack to publish events into.
D.Subscribe your continuous delivery system to an SQS queue that you also tell your CloudFormation stack to publish events into.

Answer - C
You can monitor the progress of a stack update by viewing the stack`s events. The console`s Events tab displays each major step in the creation and update of the stack sorted by the time of each event with the latest events on top. The start of the stack update process is marked with an UPDATE_IN_PROGRESS event for the stack
For more information on Monitoring your stack, please visit the below URL:
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-monitor-stack.html
Note:
Use NotificationARNs.member and when making a CreateStack call to push stack events into SNS in nearly real-time.
http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-monitor-stack.html
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/continuous-delivery-codepipeline-basic-walkthrough.html