WhatdoestheDB_FLASHBACK_RETENTION_TARGETparameterconfigure？（）

A．Anupperlimitonhowfaryoucanflashbackthedatabase，dependingontheinformationintheredologs B．Anupperlimitonhowfaryoucanflashbackthedatabase，dependingontheinformationintheundotablespace C．Theamountoftimeforwhichtheflashbackdataistobekeptintheflashrecoveryarea，providedthatthereisenoughspace D．Theamountoftimeforwhichtheflashbackdataisguaranteedtobekeptintheundotablespace，providedthatthereisenoughspace