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______。

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;