洞内中继器的标称增益为（）。
A、≤50db
B、≥50db
C、＝50db
D、0db
参考答案：B
With a lot of difficult problems ____ , the manager felt a heavy burden taken off his mind.
A．settled
B．to be settled
C．settling
D．to settle
已知一个多边形的每一个内角都等于108°，则这个多边形的边数是______．
