You use Microsoft .NET Framework 4 to create a Windows Forms application.
The application includes a RichTextBox control and a ListBox control. The ListBox control is populated with a list of valid file names.
The application allows users to drag a ListBox item to the RichTextBox control.
You need to provide a visual indication that a file that is dragged can be dropped on the RichTextBox control.
What should you do?

A.
Use a DoubleAnimation class.

B.
Use a Storyboard animation class.

C.
Use the DragDropEffects enumeration.

D.
Use the DragAction enumeration.