Inconsistency in the "Enabling Internal X509 Authentication" Lecture

When he demo the configuration file approach, he was using clusterFile
WrongConfigFile001

But when the lecturer was doing command line, he was using --PEMKeyFile:
WrongConfigFile002

Which one should we use for Homework 1.3? where we were only given THREE 3 PEM files, --PEMKeyFile obviously was needed but how about the clusterFile? do we need it in the configuration file? can we use the same server.PEM???
WrongConfigFile003

Really wonder why the lecturer blacked out a big portion of the screen when showing the configuration file!

@Wei_27563

This is a standard semantic difference (one of many) between the format for a configuration file and the options available when starting the mongod process from the command line. The documentation here shows a map of the major differences.

No, not true: