查询为' 201215121' 的同学选修过的所有课程的名字,不正确的查询语句是_______。 A. SELECT Cname FROM Course LEFT JOIN SC ON Course.Cno = SC.Cno WHERE Sno = '201215121'; B. SELECT Cname FROM Course WHERE Cno IN ( SELECT Cno FROM SC WHERE Sno = '201215121' ); C. SELECT Cname FROM Course WHERE EXISTS ( SELECT * FROM SC WHERE SC.Cno = Course.Cno AND Sno = '201215121' ); D. SELECT Cname FROM Course WHERE NOT EXISTS ( SELECT * FROM SC WHERE SC.Cno = Course.Cno AND Sno = '201215121' );