The correct answer is: A. +
The chmod command is used to change the permissions of a file or directory. The + operator is used to add permissions, while the - operator is used to remove permissions. The = operator is used to set permissions to a specific value. The % operator is used to apply permissions to all files in a directory and its subdirectories.
The following table shows the different permissions that can be assigned to a file or directory:
| Permission | Description |
|—|—|
| r | Read permission |
| w | Write permission |
| x | Execute permission |
| u | User permission |
| g | Group permission |
| o | Other permission |
For example, the following command would give the user read and write permission to the file foo.txt:
chmod u+rw foo.txt
The following command would remove the write permission from the group for the file bar.txt:
chmod g-w bar.txt
The following command would set the execute permission for all users on the directory baz:
chmod a+x baz