旧件标签悬挂在保修旧件上的时间要求是（）
A、入库前
B、入库后
C、返件前
参考答案：A
I ____ to reach the manager for the last two hours but the line is always busy. [ ]
A. tired
B. have tired
C. had tired
D. have been trying
计算机网络按功能分为（）。
A、资源子网和局域网
B、资源子网和通信子网
C、通信子网和广域网
D、局域网和广域网
