The correct answer is: A. The associated code is displayed in the Code pane.
When a user double-clicks an object in the Project pane of the Visual Basic Editor, the associated code is displayed in the Code pane. This is because the Code pane is used to view and edit the code for the objects in a project.
Option B is incorrect because the associated code is not displayed in a new window. Option C is incorrect because the object is not deleted from the Project pane. Option D is incorrect because the object's property sheet does not open.