lsvife -4 Junior Poster in Training

I created an application using ChoiceGroup.MULTIPLE..
ChoiceGroup has 7 elements and I checked/selected 5 to be deleted..
but when i press delete only 3 elements will be deleted..
here is my code..

for(int k=0;k<cg.size();k++)
{
    if(cg.isSelected(k))
    {
       cg.delete(k);
    }
}			
display.setCurrent(alert,frm);

can anybody help me??I dont know what's wrong...