You upgraded from a previous Oracle database version to Oracle Database version to Oracle Database12c. Your database supports a mixed workload. During the day, lots of insert, update, and deleteoperations are performed. At night, Extract, Transform, Load (ETL) and batch reporting jobs are run. The ETL jobs perform certain database operations using two or more concurrent sessions.After the upgrade, you notice that the performance of ETL jobs has degraded. To ascertain the cause ofperformance degradation, you want to collect basic statistics such as the level of parallelism, totaldatabase time, and the number of I/O requests for the ETL jobs. How do you accomplish this?（）

A. Examine the Active Session History (ASH) reports for the time period of the ETL or batch reporting runs.
B. Enable SQL tracing for the queries in the ETL and batch reporting queries and gather diagnostic data from the trace file.
C. Enable real-time SQL monitoring for ETL jobs and gather diagnostic data from the V$SQL_MONITOR view.
D. Enable real-time database operation monitoring using the DBMS_SQL_MONITOBEGIN_OPERATION function, and then use the DBMS_SQL_MONITOREPORT_SQL_MONITOR function to view the required information.