The correct answer is D. SaaS.
Software as a Service (SaaS) is a software distribution model in which a third-party provider hosts applications and makes them available to users over the Internet. Users do not need to install or maintain the applications on their own computers. Instead, they can access them from any device with an Internet connection.
PaaS, or Platform as a Service, is a cloud computing model that provides a platform for developing, testing, and deploying applications. PaaS providers typically offer a set of tools and services that make it easier to develop and manage applications.
IaaS, or Infrastructure as a Service, is a cloud computing model that provides access to computing resources such as servers, storage, and networking. IaaS providers typically offer a pay-as-you-go pricing model, which can be more cost-effective than traditional on-premises infrastructure.
CaaS, or Content as a Service, is a cloud computing model that provides access to content such as videos, music, and documents. CaaS providers typically offer a subscription-based pricing model.
Of the four options, SaaS is the only one that does not provision storage to most users. This is because SaaS applications are typically hosted by the provider and users do not have access to the underlying storage infrastructure.