BBU-Rru之间断链可能是由于（）
A.BBU光模块坏
B.光纤断
C.RRU断电
D.RRU坏
参考答案：A, B, C, D
《噪音》
I’ll never understand how it __________that you were late three times a week.
A．came about
B．came out
C．came across
D．came up
