You need to receive an email notification if WF1 is postponed

You create a workflow named WF1. WF1 is attached to a list named List1. You need to receive an
email notification if WF1 is postponed. What should you do?

A.
Attach an SPItemEventReceiver event receiver to List1.

B.
Attach an SPWorkflowEventReceiver event receiver to List1.

C.
Use a HandleExternalEvent activity in WF1.

D.
Use a ReceiveActivity activity in WF1.

Explanation: