which circumstances will the Diffie-Hellman key exchange allows two parties to establish a shared secret key?

Under which circumstances will the Diffie-Hellman key exchange allows two parties to establish a shared secret key? (Choose all that apply.)

A.
Over an insecure medium.

B.
After the termination of a secure session.

C.
Prior to the initiation of a secure session.

D.
After a session has been fully secured.