What function does e-mail serve?

E-mail primarily serves the function of enabling the sending and receiving of messages. It is a method of electronic communication that allows users to send written correspondence quickly and efficiently over the internet. The ability to compose, send, and receive messages is foundational to e-mail, making it an essential tool for personal and professional communication. Users can also attach files, but the core functionality revolves around message exchange.

While the other options relate to online activities, they do not accurately capture the main purpose of e-mail. Video streaming and online surveys are separate functions that utilize different technologies and platforms, while file sharing can occur through e-mail attachments but is not the primary function of e-mail itself. Therefore, option C reflects the essential role that e-mail plays in facilitating communication.