have become the most widely used form of written business communication due to their low-cost and superior speed and efficiency in communicating with both internal and external audiences.

The correct answer is Emails.

Explanation:

Email is an internet application, which allows users to exchange messages electronically or through the internet. Email is the diminutive of the word of the English word «electronic email», which in our language the possible equivalent is electronic mail; This method allows you to create, send and receive messages through electronic communication systems and at present a large part of these systems use the Internet, where "electronic email" is one of the most widely used on the net. It is important to add that emails, or at least a large part of them, allow in addition to sending text, digital documents such as videos, images, audio, among others.