The network administrator has found the following problem.The remote networks 172.16.10.0， 172.16.20.0，and 172.16.30.0 are accessed through the Central router’s serial 0/0 interface. No users are able to access172.16.20.0. After reviewing the command output shown in the graphic，what is the most likely cause of the problem？（）

• A、no gateway of last resort on Central
• B、Central router’s not receiving 172.16.20.0 update
• C、incorrect static for 172.16.20.0
• D、172.16.20.0 not located in Central’s routing table