Multiple column is single row (alpha_examall)

create or replace function alpha_examall (p_st_dt date,p_end_dt date, P_div_cd varchar2,P_dept_cd varchar2, p_desg_cd varchar2)
return varchar2
as
cursor c1 is
select distinct EXAM_INFO.exam_name
from emp_mast,EMP_EDU,EXAM_INFO
where emp_mast.emp_id=EMP_EDU.emp_id
and EMP_EDU.EXAM_CD=EXAM_INFO.EXAM_CD
and emp_mast.div_cd=P_div_cd
and emp_mast.dept_cd=P_dept_cd
and emp_mast.desg_cd=P_desg_cd
and emp_mast.flag='R'
and emp_mast.conf_fg<>'4'
and to_date(emp_mast.resig_dt) between p_st_dt and p_end_dt;

v_ret  varchar2(200) := '';

begin
for r1 in c1 loop
v_ret := v_ret||r1.exam_name||', ';
end loop;
return v_ret;
exception
when others then
return 'err';
end;