What is valid reason for using session based authentication instead of IP based authentication in a FortiGate web proxy solution?

What is valid reason for using session based authentication instead of IP based authentication in a FortiGate web proxy solution?
A . Users are required to manually enter their credentials each time they connect to a different web site.
B. Proxy users are authenticated via FSSO.
C. There are multiple users sharing the same IP address.
D. Proxy users are authenticated via RADIUS.

View Answer

Answer: C