结构化查询语言SQL — 计算机选择题

设学生选课表 SC(sno, cno, grade)，每名学生选修同一门课程至多产生一条记录。现要求查询选修了全部三门课程 C1、C2、C3 的学生学号，下列 SQL 语句正确的是（　） A. SELECT sno FROM SC WHERE cno IN ('C1','C2','C3') GROUP BY sno HAVING COUNT(*)=3 B. SELECT sno FROM SC GROUP BY sno HAVING COUNT(DISTINCT cno)=3 C. SELECT DISTINCT sno FROM SC WHERE cno='C1' AND cno='C2' AND cno='C3' D. SELECT sno FROM SC WHERE cno='C1' OR cno='C2' OR cno='C3'