单项选择题

A.Ithelpstoconfirmprojectrolesandresponsibilites,andmilestonesdates.
B.Itreducestheriskofdowntimecausedbyfacilities-relatedproblems.
C.Itensuresthatthecustomerreceivesadetailednetworkdiagram.
D.Itensuresend-usersupportimmediatelyafterthelaunchofthenewsystem.