select options query

I have defined like this :

SELECTION-SCREEN: BEGIN OF BLOCK blk WITH FRAME TITLE text-001.

SELECT-OPTIONS: s_rsnum FOR rkpf-rsnum.

SELECT-OPTIONS: s_werks FOR resb-werks.

SELECT-OPTIONS: s_matnr FOR resb-matnr.

SELECT-OPTIONS: s_bwart FOR rkpf-bwart.

SELECT-OPTIONS: s_rsdat FOR rkpf-rsdat OBLIGATORY.

SELECTION-SCREEN: END OF BLOCK blk.

still arrow is not appearing for multiple selection what can be the reason.

regards,