What is a cable modem's role in a home network, and at which OSI layer does it primarily operate when providing internet connectivity?

• A.A cable modem operates at Layer 7 (Application) and performs content inspection to enforce the ISP's acceptable use policy
• B.A cable modem operates at OSI Layer 3 (Network) and performs NAT between the home LAN subnet and the ISP's public IP address
• C.A cable modem modulates/demodulates data signals onto the cable TV coaxial infrastructure using DOCSIS (Data Over Cable Service Interface Specification), operating primarily at OSI Layer 1 (Physical) and Layer 2 (Data Link) to convert between Ethernet frames (LAN side) and DOCSIS RF signals (cable plant side)
• D.A cable modem is identical in function to a network switch, operating at Layer 2 to forward Ethernet frames between home devices