Final answer:
The user's computer knows only the public keys in terms of encryption keys.
Step-by-step explanation:
The user's computer knows only the public keys in terms of encryption keys. It does not know the private key.
When encryption is used, there are two keys involved: the public key and the private key. The public key is used to encrypt data, while the private key is used to decrypt the data. The public key can be freely shared, but the private key must be kept secret.
So, option B is the correct answer: Only the public keys.