Which of the following commands can be used to limit the amount of memory a user may use?

`umask` sets the default file permission mask for newly created files and directories.

`usermod` modifies user account properties, such as username, home directory, or shell.

The `ulimit` command allows users to view or modify shell resource limits, such as the maximum amount of virtual memory a process can use, commonly set using options like `-v`. These limits restrict various system resources available to processes, including CPU time, file size, and memory.

`passwd` is used to change a user's password.

`chage` is used to change user password expiry information.