A.SELECT学号,姓名,性别FROM s WHERE EXISTS(SELECT*FROM sc WHERE SC.学号=S.学号AND成绩<=85) B.SELECT学号,姓名,性别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,性别FROM s WHERE EXISTS(SELECT*FROM sc WHERE SC.学号=S.学号AND成绩>85) D.SELECT学号,姓名,性别FROM s WHERE NOT EXISTS(SELECT*FROM sc WHERE SC.学号=S.学号AND成绩<85)