Which complication does a NAT introduce in SDP for a SIP call? 

Answer options:

A. Additional headers due to NAT encapsulation can cause the packet size to exceed the MTU.
B. When the client is behind a NAT they may be unable to determine the appropriate offset due to time zones.
C. The IP address specified in the connection data field may be an unrouteable internal address.
D. The encryption keys advertised in the SDP are only valid for clients not behind a NAT.

D