When Are the Handshaking Stages Over in a Cryptographic System

Multiple Choice

When are the handshaking stages over in a cryptographic system standard?

A) After the two sides have authenticated each other and keys have been exchanged
B) After an electronic signature is sent and received by each party
C) After the sender encrypts the combined message and electronic signature for confidentiality
D) After the two sides have authenticated each other and messages have been exchanged