开放系统互参联参考模型(OSI)有物理层、数据链路层、网络层、会话层、表示层、应用层和()。
A.传输层
B.网络接口层
C.WEB层
D.业务层
参考答案:A
It is no longer a problem _______ the poor children in this district can go to school.
A.that
B.whether
C.so
D.because
用母联断路器并列应如何操作?