Which of the following device and interface combination…

You are purchasing a device to upgrade your network. You need to determine the type of device required, as well as the number and type of required interfaces.
The device will host three LAN subnets and a T1 Internet connection.
Which of the following device and interface combinations will support this requirement without providing any unnecessary interfaces or using subinterfaces?

A.
a switch with one Ethernet interface and three serial interfaces

B.
a router with one serial interface and three Ethernet interfaces

C.
a router with one serial interface and one Ethernet interface

D.
a switch with one modem and three serial interfaces

Explanation:
This deployment will require a router with one serial interface and three Ethernet interfaces. When LAN subnets and the Internet must be connected, you must

deploy a device that can make decisions based on IP addresses. This is the function of a router. Each LAN subnet will require a separate Ethernet interface, and
the T1 connection requires a serial interface, so the router must have one serial interface and three Ethernet interfaces.
A switch cannot be used to connect separate subnets and the Internet. This requires a router. Switches make forwarding decisions based on MAC addresses. In
this deployment, decisions must be made on the basis of IP addresses. Moreover, switches only have Ethernet interfaces, so a switch could not handle the T1
connection.
A router with one serial and one Ethernet interface will not be sufficient. Each LAN subnet will require a separate Ethernet interface.
Objective:
Network Fundamentals
Sub-Objective:
Describe the impact of infrastructure components in an enterprise network

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