Thenetworkadministratorhasfoundthefollowingproblem.Theremotenetworks172.16.10.0，172.16.20.0，and172.16.30.0areaccessedthroughtheCentralrouter’sserial0/0interface.Nousersareabletoaccess172.16.20.0.Afterreviewingthecommandoutputshowninthegraphic，whatisthemostlikelycauseoftheproblem？（）

<img src='https://img2.soutiyun.com/ask/uploadfile/2019-03-27/791d2c2699a2f4af670b044bd905bb84.jpg' /> A.nogatewayoflastresortonCentral B.Centralrouter’snotreceiving172.16.20.0update C.incorrectstaticfor172.16.20.0 D.172.16.20.0notlocatedinCentral’sroutingtable