论证为什么有且仅有14种Bravais点阵。
Which two are prerequisites for performing a flashback transaction?（） Flashback Database must be enabled.。 Undo retention guarantee for the database must be configured.。 EXECUTE privilege on the DBMS_FLASHBACK package must be granted to the user flashing back transaction.。 Supplemental logging must be enabled.。 Recycle bin must be enabled for the database.。 Block change tracking must be enabled tor the database.。
设备接头处若有相色漆，在过热后（）。 相色漆的颜色变深，漆皮裂开。 相色漆的颜色变浅，漆开始溶化。 相色漆的颜色更加明显，并有冒湿现象。
大学生社会知觉的共同特征有（） 选择性。 显著性。 投射性。 两极性。
You are using replication and the binary log files on your master server consume a lot of disk space. Which two steps should you perform to safely remove some of the older binary log files?（） Use the command PURGE BINARY LOGS and specify a binary log file name or a date and time to remove unused files。 Execute the PURGE BINARY LOGE NOT USED command。 Remove all of the binary log files that have a modification date earlier than today。 Edit the .index file to remove the files you want to delete。 Ensure that none of the attached slaves are using any of the binary logs you want to delete。
婴儿阶段（特别是2岁前）游戏的基本特征是（）
