C: During synchronization, configuration settings such as profile definitions (which include settings for things like persistence, SSL, and other traffic management features) are synchronized between the devices to ensure consistent behavior and functionality. The other options are not synchronized parameters: A. host names: Host names are typically unique to each device. B. system clocks: While having synchronized clocks is important, this is generally managed via NTP (Network Time Protocol) rather than through BIG-IP synchronization. D. VLAN failsafe settings: These settings might be part of the broader configuration but are not explicitly highlighted as synchronization parameters. E. MAC masquerade addresses: These are used in high-availability setups for failover purposes but are not typically the focus of the synchronization process.