Context-Based Access Control (CBAC) is the algorithm of the Cisco IOS firewall feature. How does CBAC improve Teleworker security?（）

A. Inbound packets are permitted only if they are part of a legitimate data flow initiated by a device on the Teleworker home network.
B. All packets are checked for integrity by analyzing their checksum.
C. Every packet is checked to see if it was sent through the VPN tunnel.
D. Every packet is inspected to see if any disallowed URLs are included. URLs are forwarded to the security cache engine for authorization.