You need to send an email notification at the end of the business process flow. 
Please select the element you should use in your flow to achieve your goal.

Answer options:

A.Step
B.Stage Transition Workflow
C.Branching
D.Global workflow
E.Stage

Correct Answer: D 
Power Automate Business process flow can include on-demand classic workflows. The classic on-demand workflow can be triggered by a business process flow stage transition or status change. 
You can add a workflow from the Components section and Composition sub-section to the stage (Number 1) or Global Workflow (Number 2) in a Business process designer. For both workflows, you need to provide a trigger. 
For the stage transition workflow, you should choose between Stage Entry and Stage Exit triggers (Number 3). And then select the workflow that you want to run (Number 4). Your workflow must be active, on-demand, and created for the same table that you are using in the stage. 

A stage transition triggers do not work for the first and the last stages in a business process flow. If you need to execute actions at these stages, you need to create a Global workflow (Number 1). 
The Global workflow is triggered by the changes in the business process (Number 2). There are four process changes: Process applied — when business process flow is started
Process abandoned — when a user abandons a business process flow, and it is archived
Process reactivated — when a user restarts an abandoned business process flow
Process completed — when a user clicks to finish the final stage and ends the business process flow.
And finally, you need to provide a workflow to run as a Global workflow (Number 3). This workflow would send an email notification at the end of the business process. 

All other options are incorrect. 
For more information about Business process flow and classic on-demand workflow integration, please visit the below URLs: 

https://docs.microsoft.com/en-us/power-automate/bpf-add-on-demand-workflow
https://docs.microsoft.com/en-us/power-automate/business-process-flows-overview#business-process-flows-that-call-a-workflow
https://docs.microsoft.com/en-us/power-automate/flow-types