Which of the following descriptions of railway business network security and reliability requirements are incorrect ?

Which of the following descriptions of railway business network security and reliability requirements are incorrect ?
A . TDM services and Ethernet services are physically isolated using different hard pipes
B . Different Ethernet subsystems use ODUk physical pipes to isolate services
C . E1 services are on the TDM plane, and IP services are on the packet plane. The encapsulation and forwarding efficiency of the two types of services are optimized.
D . Business interfaces tend to be IP-based, so physical isolation of business is no longer required

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Answer: D