To stop the PostgreSQL server, use the 'pg_ctl stop' command. If you installed the package on Linux, you would use the service or systemctl commands, but the pg_ctl command would be issued internally.
When you shut down a database, there are three modes for how connected clients and running transactions are handled, which you specify with the -m option.


If '-m smart' is specified, the system waits for all clients to terminate their connections before stopping. This was the default up to PostgreSQL version 9.4.


'-m fast' forces all client connections to be terminated and automatically rolls back any active transactions before shutting down the database. This is the default in PostgreSQL versions 9.5 and later.
'-m immediate' stops all database processes immediately without any cleanup. In this case, the database is restored to a healthy state by automatically performing a recovery operation on the next boot.


So the correct answers are C and E.