简述光中继器的作用。
参考答案：
光中继器将经过长距离衰减和畸变的信号，整形，放大，再生成一定强度的光信号继续送向前方，以保证良好的通信质量。
（）is a method used in Critical Path Methodology for constructing a project schedule network diagram that uses boxes or rectangles, referred to as nodes, to represent activities and connects them with arrows that show the logical relationships that exist between them.
A.PERT
B.AOA
C.WBS
D.PDM
“通过进度计划值和实际值的比较，发现进度推迟了”属于管理职能中的( )范畴。
A．提出问题
B．检查
C．决策
D．执行
