To answer this question, you need to understand the different events that can be triggered in a list report.
Option A) AT USER-COMMAND - This option is correct because the AT USER-COMMAND event is processed when a pushbutton with function code is clicked. This event allows you to define the logic that should be executed when the button is clicked.
Option B) AT PFn - This option is incorrect because the AT PFn event is used for function keys (such as F1, F2, etc.) on the keyboard, not for pushbuttons.
Option C) AT SELECTION-SCREEN - This option is incorrect because the AT SELECTION-SCREEN event is triggered when the selection screen is displayed, not when a pushbutton is clicked.
Option D) END-OF-SELECTION - This option is incorrect because the END-OF-SELECTION event is triggered at the end of the selection process, not when a pushbutton is clicked.
The correct answer is A) AT USER-COMMAND. This option is correct because the AT USER-COMMAND event is processed when a pushbutton with function code is clicked.