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)