You create a workflow named WF1. WF1 is attached to a list named List1.

You need to receive an e-mail notification if WF1 is postponed.

What should you do?

A.
Use a ReceiveActivity activity in WF1.

B.
Use a HandleExternalEvent activity in WF1.

C.
Attach an SPItemEventReceiver event receiver to List1.

D.
Attach an SPWorkflowEventReceiver event receiver to List1.

Explanation:
MNEMONIC RULE: “Workflow = SPWorkflowEventReceiver”

The SPWorkflowEventReceiver class handles workflow events throughout the lifetime of a workflow.

* Starting: Occurs when a workflow is starting
* Started: Occurs when a workflow is started
* Postponed: Occurs when a workflow is postponed
* Completed: Occurs when a workflow is completed

You can register the SPWorkflowEventReceiver with any site, list, or content type.

Apress – SharePoint 2010 as a Development Platform (book)