The unbind_all() method in Tkinter is used to remove all event bindings from a widget. It is a method of the widget object and can be called on any widget in the Tkinter application. Therefore, option A is the correct answer.

Option B is incorrect because the method can be called on any widget, not just the main window widget.

Option C is correct as unbind_all() does not take any parameters.

Option D is incorrect because the method only removes event bindings and does not cause the widgets to disappear.

So, the correct answers are A and C.