Routers:
a) operate at the application layer
b) operate only at the physical layer
c) cannot connect two or more networks that use the same type of cable
d) may also be called tcp/ip gateways
e) operate only at the data link layer 2

d) may also be called TCP/IP gateways

Explanation:

A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet.

Routers generally operate in the network layer of the OSI model.

Routers can connect two or more networks that use the same type of cable