虚拟网络是建立在局域网交换机或ATM交换机之上的，它以( )方式来实现逻辑工作的划分管理。
参考答案：软件
__________, they couldn’t make her change her mind.
A．Hard as they tried
B．Tried hard as they
C．As they tried hard
D．They tried as hard
A bond is needed when the bill of lading cannot be availed of the time of entry of the im- ported commodities. What does the sentence mean.（）
A. A bond is needed when the bill of lading is unavailable when the goods arrive at the destination.
B. A bond is needed when the bill of lading arrives at the port of destination.
C. A bond is not needed when the goods arrive at the destination.
D. A bond is needed when the goods arrive at the destination if there is no bill of lading at all.
