Which two statements are true regarding the use of the ssh-agent and ssh-add commands?

Which two statements are true regarding the use of the ssh-agent and ssh-add commands?

A.
The ssh-agent is used to hold private keys.

B.
The ssh-add command retries the most recently saved passphrase if multiple key files
are used.

C.
The ssh-add command asks for the passphrase only the first time a key is required by
the same user in the same shell.

D.
The ssh-add command may ask for a passphrase each time the same key is required by
the same user in the same shell.

E.
The ssh-agent is used to hold only public keys.