Final answer:
To protect a database with a password, it must be open for exclusive use. This prevents access by other users and ensures security during password application.
Step-by-step explanation:
In order to protect a database with a password, the correct answer would be a) Exclusive use. When a database is open for exclusive use, it means that no other users can access it while changes are being made, including security changes such as applying a password. This is necessary to ensure that there are no conflicts or security breaches during the process of password protection.