What are the three main service models of cloud computing?

Software as a Service $($SaaS$),$ Platform as a Service $($PaaS$),$ Infrastructure as a Service $($IaaS$)$

Software as a Service $($SaaS$),$ Platform as a Service $($PaaS$),$ Internet as a Service $($IaaS$)$

Software as a Service $($SaaS$),$ Product as a Service $($PaaS$),$ Infrastructure as a Service $($IaaS$)$

Software as a Service $($SaaS$),$ Platform as a Service $($PaaS$),$ Information as a Service $($IaaS$)$