A.
select s.sname,c.cname from stu as s,class c where s.cid=c.cid;
B.
select stu.sname,class.cname from stu as s,class c where s.cid=c.cid;
C.
select s.sname,c.cname from stu as s,class c where stu.cid=class.cid;
D.
select stu.sname,class.cname from stu as s,class c where stu.cid=class.cid;