查询选修了课程号为'C2'的学生号和姓名，若用下列SQL的SELECT语句表达时，错

问题：

查询选修了课程号为'C2'的学生号和姓名，若用下列SQL的SELECT语句表达时，错误的是( )。

A．SELECT S#，SNAME FROM S WHERE S# =(SELECT SS# FROM SC WHERE C#='C2')

B．SELECT S#,SNAME FROM S，SC WHERE S#==SS# AND C#='C2'

C．SELECT S#，SNAME FROM S，SC WHERE S#=SS# AND C#='C2' ORDER BY S#

D．SELECT S#，SNAME FROM S WHERE S IN (SELECT SS## FROM SC WHERE C#='C2')