check is good activate i gert err

REPORT test.

SELECTION-SCREEN BEGIN OF SCREEN 100 AS WINDOW TITLE text-100.

PARAMETERS: button1 RADIOBUTTON GROUP grp,

button2 RADIOBUTTON GROUP grp,

button3 RADIOBUTTON GROUP grp,

button4 RADIOBUTTON GROUP grp.

SELECTION-SCREEN END OF SCREEN 100.

why?????

err-when genarating the selection screen 100