微波背景辐射
参考答案：
来自宇宙空间背景上的各向同性的微波辐射。它是一种充满整个宇宙的电磁辐射。
A control chart has all of the following characteristics EXCEPT:
A) It illustrates how a process behaves over time.B) It is used to determine whether or not a process is stable or has predictable performance.C) It illustrates how various factors might be linked to potential problems or effects.D) It can be used to monitor any type of output variable.
ONU的LAN1-4口指示灯常亮表示（）。
A.以太网口连接正常
B.以太网口有数据传输
C.没有建立以太网连接
D.以上皆错
