A.SELECTS. S#,SNAMEFROM S WHERE S. S#=(SELECTSC)S# FROM SC WHERE C#=’C2’
B.SELECTS.S#,SNAMEFROMS,SC WHERES.S#=SC.S# AND C#=’C2’
C.SELECTS.S#,SNAME FROM S,SC WHERES.S#=SC.S# AND C#=’C2’ORDER BY S.S#
D.SELECTS.S#,SNAME FROM S WHERE S.S# IN (SELECT SC) S# FROM SC WHERE C#=’C2’