下列状态哪一个不是生成树协议的端口状态？（）。
A.Learning
B.Blocking
C.Listening
D.Working
参考答案：D
With the guide________the way, we finally got to the village which we were looking for. [ ]
A. led
B. leading
C. to lead
D. had led
重大质量事故由( )组织进行调查。
A．项目法人
B．项目主管部门
C．省级以上水行政主管部门
D．水利部
