A.
select sname from student, sc where student.sno=sc.sno and cno !='C002'
B.
select sname from student where sno not in (select sno from sc where cno='C002')
C.
select sname from student where exixts (select * from sc where student.sno=sc.sno and cno<>'C002')
D.
select sname from student where not exixts (select * from sc where student.sno=sc.sno and cno='C002')