pg_config is a command that displays a variety of information about PostgreSQL that is installed, including the parameters used to build the server.
pg_controldata is a command that displays information initialized by initdb, such as the catalog version.
pg_ctl can start, stop, and restart the database server, display the status of a running server, and reload configuration files.
pg_isready is a command that checks the status of the PostgreSQL server, returning an exit status indicating whether it is ready for connection.
pg_resetwal is a command that can remove PostgreSQL's WAL (write-ahead log) and also initialize some of the control information stored in the pg_control file, and can be used as a last resort when the server cannot be started, for example due to corruption of files.

So the correct answers are C, D, and E.