YourdatabaseisrunningunderautomaticundomanagementandtheUNDO_RETENTIONparameterissetto900sec.Youexecutedthefollowingcommandtoenableretentionguarantee：SQL＞ALTERTABLESPACEundotbs1RETENTIONGUARANTEEWhateffectwouldthisstatementhaveonthedatabase？（）

A．Theextentsinundotablespaceretaindatauntilthenextfulldatabasebackup. B．Theextentscontainingcommitteddataintheundotablespaceareneveroverwritten. C．Theextentswhichnolongercontainuncommitteddataintheundotablespacearenotoverwrittenforatleast15minutes. D．Theextentscontainingcommitteddataintheundotablespacearenotoverwrittenuntiltheinstanceisshutdown.