The following release pipeline has been defined in Azure DevOps. 

The Artifacts section has been defined to pick up the artifacts from a build pipeline defined in Azure DevOps. 
You have to configure the pipeline to ensure that an approval is required before the build can be released to the “Production” stage. Which of the following would you implement to fulfill this requirement?

Answer options:

A.Add a gate to the “Staging” stage.
B.Add a gate to the “Production” stage.
C.Add an approval to “Production” stage.
D.Add a task to the “Production” stage.

Answer – C 
You can easily perform this requirement by adding an approval to the “Production” stage, as shown below. 

First modify the pre-stage configuration
Enable “Pre-deployment approvals”
Enter the approvers for the stage
Since this is clear from the implementation, all other options are incorrect. 
For more information on defining an approval, please visit the following URL- 

https://docs.microsoft.com/en-us/azure/devops/pipelines/release/approvals/approvals?view=azure-devops