将SC表中所有选修了"Maths"课程，但成绩低于该课程平均分的选课记录全部删除，下列选项中最合适的SQL语句为________。
A. delete from SC where Grade<(select AVG(Grade) from SC where Cname = 'Maths');
B. delete from SC whereCname = 'Maths' and Grade<(select AVG(Grade) from SC);
C. delete from SC whereCname = 'Maths' and Grade<(select AVG(Grade) from SC where Cname = 'Maths');
D. delete from SC where Cname = 'Maths' and Grade < AVG(Grade);
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查询平均成绩大于等于 60 分的所有学生的学号、姓名和个人平均成绩，下列选项中 最合适的SQL语句为________。
A. select S.Sno, Sname, AVG(Grade) avg_grade from Student as S, SC where S.Sno = SC.Sno group by S.Sno having avg_grade > 60;
B. select S.Sno, Sname, AVG(Grade) avg_grade from Student as S, SC where S.Sno = SC.Sno group by S.Sno having AVG(Grade) > 60;
C. select S.Sno, Sname, AVG(Grade) avg_grade from Student as S, SC where S.Sno = SC.Sno and avg_grade > 60;
D. select S.Sno, Sname, AVG(Grade) avg_grade from Student as S, SC where S.Sno = SC.Sno and AVG(Grade) > 60;
查询没有选修"张三"同学所选修的任意一门课程的学生姓名，下列选项中最合适的语句是________。
A. selectSnamefromStudentexceptselectSnamefromStudent,SCwhereStudent.Sno=SC.SnoandSC.Cnoin(selectCnofromStudent,SCwhereStudent.Sno=SC.SnoandStudent.Sname='张三');
B. selectSnamefromStudentexceptselectSnamefromStudent,SCwhereStudent.Sno=SC.SnoandStudent.Sname='张三';
C. selectSnamefromStudent,SCwhereStudent.Sno=SC.SnoandSC.Cnonotin(selectCnofromStudent,SCwhereStudent.Sno=SC.SnoandStudent.Sname='张三');
D. selectSnamefromStudent,SCwhereStudent.Sno=SC.SnoandSC.Cno<>(selectCnofromStudent,SCwhereStudent.Sno=SC.SnoandStudent.Sname='张三');
基于教材上的学生表Student、课程表Course和选课表SC，查找选修了课程“C2”的学生中成绩最高的学生的学号，正确的SQL语句是________。
A. SELECTSnoFORMSCWHERECno='C2'andGrade=(SELECTMAX(Grade)FORMSCWHERECno='C2')
B. SELECTSnoFORMSCWHERECno='C2'andGradeIN(SELECTGradeFORMSCWHERECno='C2')
C. SELECTSno,MAX(Grade)FORMSCWHERECno='C2'
D. SELECTSnoFROMSCWHERECno='C2'andGrade>=ALL(SELECTGradeFROMSCWHERECno='C2')
内胚层分化为:
A. 气管和主支气管、肺的上皮
B. 消化管、消化腺的上皮
C. 心血管系统的上皮
D. 膀胱、尿道的上皮
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