Which three actions are performed by Database Upgrade Assistant (DBUA)? (Choose three.) 

Answer options:

A. It recompiles all stored PL/SQL code by using utlrp.sql.
B. It empties the RECYCLE BIN.
C. It performs prerequisite checks to verify if the Oracle database is ready for upgrade.
D. It sets all user tablespaces to read-only before starting the upgrade.
E. It removes the AUDSYS schema and the AUDIT_ADMIN and AUDIT_VIEWER roles
F. It increases tablespace size, if required, to meet upgrade requirements.

ACF

Reference: https://oracle-base.com/articles/12c/upgrading-to-12c