Final answer:
Routers, protocols, and switches all play a role in directing signals over the internet.
Step-by-step explanation:
The correct answer is d) All of the above. Routers, protocols, and switches all play a role in directing signals over the internet. Routers are devices that help in directing network traffic between different networks, such as the internet. Protocols are a set of rules that govern how data is transmitted over a network, and they ensure that the data is delivered accurately. Switches are used to connect devices within a network and help in forwarding data packets to the correct destination.