What is a virtual firewall？（）

• A、another name for a firewall deployed in routed mode
• B、another name for a firewall deployed in transparent mode
• C、a separation of multiple firewall security contexts on a single firewall
• D、a firewall that， when deployed in routed mode， can support up to 1000 VLANs per context
• E、a firewall that has multiple contexts， all of which share the same policies （such as NAT and ACLs）