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

umask sets the default file permissions for newly created files and directories, not memory limits.

usermod is used to modify user account properties, such as username, home directory, or shell, but not runtime resource limits like memory.

The ulimit command allows users and system administrators to control resource limits, such as memory usage (e.g., using -m for virtual memory or -v for data segment size) and CPU time, for processes started from the current shell session. These limits prevent processes from consuming excessive system resources and affecting overall system stability.

passwd is used to change a user's password.

chage is used to change user password expiry information.