My English teacher has______ rich experience in teaching and we all think she is ______ experienced teacher.

A．不填; an

B．a; an

C．不填; the

D．a;the

平行导坑一般设在地下水的（）。

A、下游一侧

B、地下水源来源一侧

C、远离主洞

D、两侧都可以