感染根管内常见的优势菌包括（）
A.放线菌
B.牙髓卟啉单胞菌
C.牙龈卟啉单胞菌
D.梭形杆菌
E.乳酸杆菌
参考答案：B
By the time they got to the quake-stricken area, the rescuers___________what difficulty they would have helping the victims out.
A．sensed
B．had sensed
C．had been sensing
D．were sensing
依据《工程测量规范》三等水准测量测站前后视距的累积差不大于（）
A.5m
B.10m
C.3m
D.6m
