You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. The application uses the drag-and-drop functionality. You need to ensure that the drag-and-drop operation is stopped when a user moves the cursor outside the boundaries of the application form. Which enumeration member should you use?（）

• A、 DragAction.Cancel
• B、 DragAction.Drop
• C、 DragDropEffects.None
• D、 DragDropEffects.All