What role does zero knowledge proof have in cryptography?

A.
The entity that needs to prove that he has access to a specific key needs to provide the key to the other entity

B.
It carries out authentication to a verifier

C.
It ensures that a verifier can prove to others that the sender has the correct key

D.
It allows the verifier to gain access to an authentication key

Explanation:
If a sender encrypts something with his private key, you will verify
that his private key was used by decrypting the data with his public key. The sender
is authenticating to the verifier, but the verifier cannot use this information to
prove to any other entity that the sender truly has the correct private key.