private void btn_back_Click(object sender, EventArgs e)
 {
     if (Globle_data.student_selected_language.CompareTo("number") == 0)
     {
         frm_student_option lo = new frm_student_option();
         lo.Show();
         this.Hide();
     }
     else
     {
         frm_language_option lo = new frm_language_option();
         lo.Show();
         this.Hide();
     }
 }
        private void button2_Click(object sender, EventArgs e)
        {
            try
            {
                Globle_data.student_selected_option = "test";
                frm_language_option lo = new frm_language_option();
                lo.Show();

                this.Hide();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
        }