Which of the following is a valid source for Windows operating system updates?

SNA (Systems Network Architecture) is an outdated networking architecture developed by IBM and is not a source for Windows operating system updates.

RIS (Remote Installation Services) was a Windows Server feature used for network-based operating system deployment, not for ongoing update management.

RAS (Remote Access Service) allows users to connect remotely to a network and does not provide operating system updates.

WSUS (Windows Server Update Services) is a Microsoft server role that enables administrators to manage and distribute updates for Microsoft products, including Windows operating systems, to computers on their network. It acts as a centralized repository for updates, offering control over the deployment process.