Combo box and list box not displaying output

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C#

combobox

ListBox

So im making a form application program for a MEWS System which displays vital sign results for a patient at a hospital. Im using a combo box and list box to select the vital sign number and display the score in the list box. I entered in the code but when I run the program it doesnt display the options in the combo box. Whats wrong with my code

private void cbxRespScore_SelectedIndexChanged(object sender, EventArgs e)
        {


            ta = cbxRespScore.SelectedItem.ToString();

            if (ta == "0")
            {

                lbxRespScore.Items.Clear();
                lbxRespScore.Items.Add("3");

            }
            else if (ta == "<40")
            {
                lbxRespScore.Items.Clear();
                lbxRespScore.Items.Add("2");

            }
            else if (ta == "41-50")
            {
                lbxRespScore.Items.Clear();
                lbxRespScore.Items.Add("1");

            }
            else if (ta == "51-100")
            {
                lbxRespScore.Items.Clear();
                lbxRespScore.Items.Add("0");

            }
            else if (ta == "101-110")
            {
                lbxRespScore.Items.Clear();
                lbxRespScore.Items.Add("1");

            }

            else if (ta == "111-130")
            {
                lbxRespScore.Items.Clear();
                lbxRespScore.Items.Add("2");

            }

            else if (ta == ">131")
            {
                lbxRespScore.Items.Clear();
                lbxRespScore.Items.Add("3");

            }



        }