You want to analyze a SQL Tuning Set （STS） using SQL Performance Analyzer in a test database. Which two statements are true regarding the activities performed during the test execution of SQLs in a SQL Tuning Set？（）

• A、 Every SQL statement in the STS is considered only once for execution.
• B、 The SQL statements in the STS are executed concurrently to produce the execution plan and execution statistics.
• C、 The execution plan and execution statistics are computed for each SQL statement in the STS. 
• D、 The effects of DDL and DML are considered to produce the execution plan and execution statistics.