The correct answer is: A. Shadow
The shadow file is a system file that contains the encrypted passwords of all users on a Linux system. It is used to store the passwords in a secure location, and to prevent users from accessing them directly. The shadow file is typically located in the /etc directory.
The password file is a system file that contains the usernames and passwords of all users on a Linux system. It is used to authenticate users when they log in to the system. The password file is typically located in the /etc directory.
The profile file is a system file that contains information about a user’s environment, such as their home directory, shell, and PATH. It is used to set up the user’s environment when they log in to the system. The profile file is typically located in the /etc/skel directory.
Therefore, the shadow file is the only file that contains information related to password aging.