What is true about a background engine? （）(Choose two.)

• A、It is a server-side PL/SQL procedure.
• B、When executing a PL/SQL function activity, it will automatically ping (cache) the PL/SQL code.
• C、It executes deferred activities in decreasing order of their Cost property value (activities with higher cost value are processed first).
• D、It would fail if another background engine process is started to handle the same type of activities within the same item type.
• E、During its single invocation, it processes activities that were stuck, deferred or timed out when the background engine was started.