单项选择题
YouexecutedthefollowingcommandinRecoveryManager（RMAN）againstyourOracle10gdatabase：RMAN>REPORTNEEDBACKUPdays3；Whatwouldbetheoutputofthiscommand？（）
A.alistoffilesthatrequireabackupwithinthreedays
B.alistoffilesthathavenotbeenbackedupforthreedays
C.alistoffilesthatRMANrecommendsbebackeduponlyonceineverythreedays，basedonlowvolatility
D.alistoffilesforwhichabackuphasalreadybeenperformedandmayneedabackupafterthreedays