Email is the transmission of messages and files between computers or smart devices over a(n) ____.

A) STMP
B) network
C) ISP
D) Web app

A network is a group of interconnected devices that can communicate with each other. Email messages and files are transmitted between computers or smart devices over a network, making B the correct choice. SMTP is a protocol used for sending email, not for transmitting messages and files over a network. ISP is a service provider that provides internet connectivity, but it is not directly related to email transmission. A web app is a software application that runs on a web server and is accessed through a web browser, and while email can be accessed through a web app, it is not the method by which messages and files are transmitted between devices.