在学生选课表(SC)中，查询选修了3号课程(课程号CH)的学生的学号(XH)及其成绩(GD)。查询结果按分数的降序排列。实现该功能的正确SQL语句是( )。

A．SELECT XH，GD FROM SC WHERE CH='3'ORDER BY GD DESC
B．SELECT XH，GD FROM SC WHERE CH='3'ORDER BY GD ASC
C．SELECT XH，GD FROM SC WHERE CH='3'GROUP BY GD DESC
D．SELECT XH，GD FROM SC WHERE CH='3'GROUP BY GD ASC