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 )