Google Apps is a set of online applications allowing users to create and share documents and spreadsheets. This is an example of:

Platform as a Service (PaaS) provides a development and deployment environment for building applications, not ready-made applications for end users such as word processors or spreadsheets.

Software as a Service (SaaS) provides fully managed, hosted applications that users access directly through a browser or thin client without managing any underlying infrastructure, platform, or runtime. Google Apps (now Google Workspace) matches this model exactly - users create and share documents without installing software or managing servers. The provider handles all maintenance, updates, and infrastructure.

Infrastructure as a Service (IaaS) provides virtualized compute, storage, and networking resources for IT teams to build upon, not consumer-facing productivity applications.

SaaS is clearly the correct cloud service model for this scenario, so 'None of the above' is incorrect.