What is a type of local network that people can use to access the Internet?
Computer
Mobile
Public Wi-Fi
Router

Id say Router is the answer based on your Question.

Router - is a device used to host a network signal which people will require the SSID(network-name) to connect to.

It is a bit confusing because the correct answer is SSID  which leads me to belive Public Wi-Fi is also correct..

answer unified communications;

(a) oldest