假定学生信息表是student(sid, sname, sex, age),课程信息表是course(cid, cname, teacher),学生选课信息表是sc(sid, cid, grade),查询没有参加考试的学生名单,以下语句正确的是()
A. select sname from student where sid in (select sid from sc);
B. select sname from student where sid not in (select sid from sc);
C. select sname from student;
D. select sid from sc;
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