Which of the following choices below contains all the messages that SIP is required to act on during the request/response handshake?

Which of the following choices below contains all the messages that SIP is required to act on during the request/response handshake?
A . INVITE, 200 OK and ACK
B . INVITE, 200 O
C . ACK and 200 ACCEPTED
D . INVIT
E . 200 OK
F . INVITE, 200 OK and 200 ACCEPTED

Answer: A

Explanation:

Reference: http://www.brocade.com/downloads/documents/html_product_manuals/SI_12502_ASLBG/wwhelp/wwhimpl/common/html/wwhelp.htm#context=SI_12502_ASLB_Guide&file=sip.3.2. html