Which of the following will change the group that is associated with a file?

'chmod' modifies file permission bits (read, write, execute) and does not change group ownership.

'chmod -w' removes write permissions from a file and has no effect on group association.

'chown' changes both the owner and group of a file. To change only the group, you use 'chown :groupname filename' or 'chown owner:groupname filename'. It directly modifies the group association stored in the file's inode metadata, which is what the question requires.

'ls -g' is a listing command that displays group information but does not change anything.