单项选择题 Youcreateatableinyourdatabasethatcontains50，000rowsapproximately.Thequeriesperformedonthetablearecomplexandperformedonthetablefrequently.Whichadvisorhelpsyouachievethebestperformanceofdatabaseforqueriesbyrecommendingtheappropriateindexes？（）

单项选择题 You want to check all the data blocks being written to the datafiles by analyzing the data on each block every time the DBWn process writes.   Which action will you perform to check the data blocks？（）

单项选择题 William specified the following initialization parameter settings in the pfile：   BACKGROUND_DUMP_DEST = ’u01\oradata\dir_A’   USER_DUMP_DEST = ’u01\oradata\dir_B’   DB_CREATE_FILE_DEST = ’u01\oradata\dir_C’   DB_CREATE_ONLINE_LOG_DEST_n = ’u01\oradata\dir_D’   William enabled the change-tracking feature because he does not want to scan the entire datafile during backup. What is the default storage location for the change tracking file？（）