Of the ways listed, which is the best method to temporarily suspend a user's ability to interactively login?

Using `passwd -d username` removes the user's password, which prevents password-based login but does not explicitly suspend the account and might not be suitable for temporary measures.

The `chage` command (change user password expiry information) allows an administrator to set an account expiration date, effectively disabling the user account from logging in until the expiration date is removed or modified. This provides a temporary and reversible suspension of login privileges without altering the user's password or home directory configuration.

Changing the user's password prevents the user from logging in with their old password but does not suspend the account itself; a new password could be provided, or other authentication methods might still work.

Adding `exit` to a user's .login file (or similar shell configuration) is a workaround that depends on the shell and login method, and it is not a standard or robust way to temporarily disable an account at the system level.