At 5：30 PM， a database administrator， William， is informed that an important record of employee no E0025 is missing from the SCOTT.EMPLOYEE table. At 4：30 P.M， the table contained the record of employee no E0025. William issues the following command to find the SQL statements that are used to undo the deletion： SELECT operation， undo_sql， logon_user FROM FLASHBACK_TRANSACTION_QUERY WHERE xid= HEXTORAW（’0100043E23456’）； where ’0100043E23456’ is the transaction ID of the transaction that deleted the row. Before issuing the above statement， which task did William perform to identify the transaction ID of the transaction that deleted the row？（） William used the Flashback Version Query feature.。 William issued the CROSSCHECK command at the RMAN prompt.。 William viewed the alert log file.。 William used the Flashback Table feature.。
液体动压轴承工作时，（）与平衡轴的载荷、使轴浮在油中无关。 有足够的供油压力。 有一定的压力差。 使轴有一定的旋转速度。 有足够的轴向力。
Which statements are true regarding the USERS tablespace（） A bitmap is used to record free extents.。 Free extents information is managed within the tablespace.。 Free extents information is managed in the SYSAUX tablespace.。 The data dictionary tables are updated when extents are allocated or deallocated。
同步电动机异步起动时，励磁绕组应（）。 开路。 短路。 通过大电阻短路。 通过大电抗短路。
Which statement is true？（） Compilation fails.。 An exception is thrown at runtime.。 Synchronizing the run（） method would make the class thread-safe.。 The data in variable "x" are protected from concurrent access problems.。 Declaring the doThings（） method as static would make the class thread-safe.。 Wrapping the statements within doThings（） in a synchronized（new Object（））{} block would make the class thread-safe.。
王某，17岁。溺水后被人救起，现场立即进行心肺复苏，送往医院心电图显示有心室纤颤，最有效的除颤方法是（）
