Which of the following best defines Software as a Service (SaaS)?

The definition of Software as a Service (SaaS) is indeed best captured by the description of it as a model for delivering software applications over the internet. This approach allows users to access software applications from any device with an internet connection without the need for local installation.

SaaS typically involves a subscription-based model where users can use the software on a pay-as-you-go basis. The applications are hosted in the cloud by the service provider, which means that maintenance, security, and upgrades are handled by the provider, relieving users from the traditional burdens of software management.

Other choices do not accurately describe SaaS. Mentioning a service for managing virtual machines pertains more to Infrastructure as a Service (IaaS), which focuses on delivering virtualized computing resources over the internet. A standard for network protocols refers to technical specifications that facilitate communication among network devices, while a framework for building software suggests a more foundational level of software development, which does not align with the characteristics of SaaS.