A.SELECT S.S#,SNAME FROM S WHERE S.S#<br> (SELECT SC. S# FROM SC WHERE C#='C2')
B.SELECT S.S#,SNAME FROMS,SC<br> WHERE S.S#=SC.S# AND C#='C2' C.SELECT S.S#,SNAME FROM S,SC<br> &nb D.SELECTS.S#,SNAME FROM S WHERE S.S#<br> IN(SELECT SC. S# FROM SC WHERE C#='C2')