题目内容
（请给出正确答案）
[主观题]
The teacher ______ for a few seconds till he found proper words to make his idea clearer
A. broke off
B. broke through
C. broke out
D. broke into
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对于教学数据库的三个基本表：S(Sno，Sname，Ssex)，SC(Sno，Cno，Grade)，C(Cno，Cname， Teacher)，其中S为学生表，SC为学生选课表，C为课程表，则对于语句：检索至少选修LIU老师所授课课程中一门课程的女生姓名，SQL语句错误的是______。
A) SELECT Sname
FROM S，SC，C
WHERE S.Sno=SC.Sno AND SC.Cno=C.Cno AND Teacher=‘LIU’AND Ssex=‘F’
B) SELECT Sname
FROM S WHERE Ssex=‘F’AND Sno IN
(SELECT Sno
FROM SC
WHERE Cno IN(SELECT Cno FROM C
WHERE Teacher=‘LIU’))
C) SELECT Sname
FROM S WHERE Ssex=‘F’AND EXISTS (SELECT*
FROM SC
WHERE SC.Sno=S.Sno AND EXISTS
(SELECT*
FROM C
WHERE Teacher=‘LIU’))
D) SELECT Sname
FROM S WHERE Ssex=‘F’AND EXISTS(SELECT*
FROM SC
WHERE SC.Sno=S.Sno AND EXISTS
(SELECT*
FROM C
WHERE C.Cno=SC.Cno AND Teacher=‘LIU’))
