How do you program an input validation on a selection screen that allows users to correct their input?

A. Implement the check at the event AT SELECTION-SCREEN OUTPUT. In case of an input error, a type E MESSAGE must be displayed.

B. Implement a check at the event AT SELECTION-SCREEN. In case of an input error, a type E MESSAGE must be displayed.

C. Implement the check at the event END-OF-SELECTION. In case of an input error, a type E MESSAGE must be displayed.

D. Implement the check at the event AT SELECTION-SCREEN. In case of an input error, a type A MESSAGE must be displayed.