共用题干题AstuteserviceprovidersrealizethatthecontinuedsupportoflegacyX.25andasynchronousnetworkelementusingseparateoperationsnetworkiscost(16).Forexample,themaintenanceofmultiplenetworkscanrequireadditionalstaff.Often,thisstaffmustbetrainedonmultiplevendortechnologies,sometimesrequiringparallelgroupsspecializingineach(17).Hence,additionalmaintenanceproceduresmustbemaintainedandadministrativerecordsare(18).Theduplicationoftransportfacilitiestocarry(19)networktrafficisaninefficientuseofresources.Andnotsurprisingly,moretechnologiesinstalledinacentralofficemeansthenecessityformorephysicalspace,andanincreaseinpowerconnectionsandpowerconsumptionmigrationofthese(20)networkelementstoIP-basedDCnsisalogicalstrategy.
空白处（19）应选择（）
A.overlook
B.overlie
C.overlay
D.overleap