A.SELECT学号,姓名FROM S WHERE NOT EXISTS; (SELECT*FROM SC WHERE SC.学号=S.学号AND成绩<85) B.SELECT学号,姓名FROM S WHERE NOT EXISTS; (SELECT*FROM SC WHERE SC.学号=S.学号AND成绩>=85) C.SELECT学号,姓名FROM S,SC WHERE S.学号=SC.学号AND成绩>=85 D.SELECT学号,姓名FROM S,SC WHERE S.学号=SC.学号AND ALL成绩>=85