What is the benefit of running the catctl.pl script during an upgrade of a pre-12c database to an Oracle 12c database? 

Answer options:

A. It provides a summary of the upgrade results.
B. It recompiles all invalid PL/SQL and Java code.
C. It generates a log file containing the fixes that can be made to the source database.
D. It provides parallel upgrade options to finish the upgrade process with a reduced down time.
E. It generates fix-up scripts to be run on the source database before upgrade.

D

References: https://docs.oracle.com/database/121/UPGRD/upgrade.htm#UPGRD52860