Which of the following commands is used to set restrictions on the size of a core file that is created for a user when a program crashes?

`core` is not a standard command for managing resource limits or core file sizes; 'core' refers to the core dump file itself.

`edquota` is used to edit user and group disk quotas, which are related to disk space usage for files in general, not specifically core file size limits.

The `ulimit` command, with the -c option, allows an administrator or user to set the maximum size of a core dump file (core file size) that can be generated by a process. This restriction prevents large core files from consuming excessive disk space when a program crashes.

`quota` is used to display disk usage and quotas for users or groups, but not to set process resource limits like core file size.