You need to create work items and manage notifications for your project from Microsoft Teams. You consider using the Azure Boards app for Microsoft Teams. 
What should you do to make this work?

Answer options:

A.Create a service principal
B.Enable Allow public projects
C.Create a service hook
D.Enable third-party application access via OAuth
E.Create a new security group

Correct Answer: D 
Azure DevOps integrates with several Microsoft and third-party applications like GitHub, Jira, Teams, Slack, ServiceNow, etc. 
You can use Service hooks for Azure DevOps integration with a list of third-party applications and services. The Service hooks subscription is broadcasting the Azure DevOps events to other services. But when you need more features like managing the work items in Microsoft Teams or Slack channels instead of receiving only a notification, Microsoft recommends using the apps for each service like Azure Boards app for Teams or Azure Boards app for Slack. There are also apps for Azure Pipelines and Azure Repos for both applications. 
But before you start using these apps and manage notifications, you need to be sure that a security policy for application connection for your Azure DevOps organization is enabled. You need to open an Organization Settings (Number 1) and on the Policies screen (Number 2) set to On the “Third-party application access via OAuth” option for application connection policies (Number 3). 

After that, you are set for managing items and Azure DevOps notifications with Azure Boards app for Microsoft Teams or Slack. Suppose your Organization settings applications connection policy for the third-party applications to use OAuth is not enabled. In that case, you will receive an error “Sorry, something went wrong. Please try again” when you try to manage notifications from the apps. 
All other options are incorrect.
For more information about using the Azure Board app for Microsoft Teams, please visit the below URLs: 

https://docs.microsoft.com/en-us/azure/devops/boards/integrations/boards-teams?toc=%2Fazure%2Fdevops%2Fmarketplace-extensibility%2Ftoc.json&bc=%2Fazure%2Fdevops%2Fmarketplace-extensibility%2Fbreadcrumb%2Ftoc.json&view=azure-devops
https://docs.microsoft.com/en-us/azure/devops/organizations/accounts/change-application-access-policies?view=azure-devops
https://docs.microsoft.com/en-us/azure/devops/service-hooks/services/teams?view=azure-devops