To send data to Google Analytics from a web-connected device like a point-of-sale system, what feature must be used?

The Measurement Protocol is the correct answer because it's a set of rules for collecting hits from any internet-connected device and sending them to Google Analytics. This allows data from non-website sources, like point-of-sale systems, kiosks, or other IoT devices, to be integrated into your GA reports. Data Import is used to upload data from external sources (like CRM data) to enrich existing GA data, not to send hits directly. Browser cookies are used by standard website tracking to store user information, but they are not a mechanism for sending data from non-browser devices. The Networking protocol is a general term for communication rules on a network and is not specific to Google Analytics data collection.