题目：查询选修了a001号课程的学生的最高成绩（）
A、select cid, max(grade) from course where cid=’a001’ group by cid
B、select cid,max(grade) from student where cid=’a001’ group by cid
C、select cid, max(grade) from sc where cid=’a001’ group by cid
D、select cid, max(grade) from student group by cid having cid=’a001’
