A Set the AsyncPostBackTrigger attribute of the UpdatePanel to the ID of the Button control.
B Set the AsyncPostBackTrigger attribute of the Button control to the ID of the UpdatePanel.
C Add a Trigger control to the AsyncPostBackTriggers section of the UpdatePanel. Set the ControlID attribute of the Trigger control to the ID of the Button control.
D Add an AsyncPostBackTrigger control to the Triggers section of the UpdatePanel. Set the ControlID attribute of the AsyncPostBackTrigger control to the ID of the Button
control.