与妇女月经关系密切的是（）
A、督脉
B、任脉
C、冲脉
D、带脉
E、维脉
参考答案：C
从学生社会群体来考虑，学生违规的原因有哪些？
--- I wonder how much you charge for your service.
--- The first two are free ______ the third costs $30.
A．while
B．until
C．when
D．before
