阅读以下短文，回答98-100题。 (IPv6 is not interoperable with IPv4，In essence.it establishes a parallel version of the Internet not directly accessible with IPv4 sofeware.This means softwate upgrades or translator facilities are necessary for networking devices that need to communicate on both networks.Most modern computer operating systems already support both versions of the Internet Protocal.Network infrastrutures，however，are still lagging in this development.Aside form the complex array of physical connections that make up its infrastrure，the Internet is facilitated by bi- or multi-lateral commercial contracts(e.g. pearing agreements)，and by technical spesifications or protocals that describe how to exchange data over the network.Indeed，the Internet is defined by its interconnections and routing policies.) Based on the paragraph above， it is shown that in order to deploy IPv6 protocol on the Internet，（）has to be built. The network devices which need to communicate with both networks are required to have upgraded software or （）in the movement of IPv4 to IPv6 transition，（）are relatively slow in this event.

A．separated network

B．mobile network

C．access network

D．radio network

A．IPv6 software

B．translator facilities

C．operating systems

D．IPv4 software

A．IPv4 network

B．translator facilities

C．operating systems

D．network infrastructures