When configuring a FortiGate in a multi-WAN setup, why would an administrator enable session preservation...

To allow the FortiGate to dynamically change interfaces for all active sessions when a WAN link fails

To make sure all sessions without source NAT enabled always use the primary WAN link

To improve security by forcing users to authenticate again when the WAN link changes

To ensure that existing SSL VPN connections remain on the same interface even if route changes occur