Answer:
The file can be read only by a user with the decryption key
Explanation:
The way encryption works is it scrambles the data in a file following the rules of the encryption algorithm using a certain key to tell it how to scramble everything.
Without the key, the computer doesn't know how to decrypt it.
This is true no matter who has access to the file, be it a system administrator, a hacker, or even a legitimate user who has somehow lost access to the key
Strictly speaking, encryption <em>can</em> be broken, but, especially with modern encryption, that's a matter of centuries, and isn't really feasible