Explanation:

The correct option is (d) Allotment of electromagnetic spectrum. Cloud computing services primarily refer to the delivery of on-demand computing resources over the internet, typically categorized into three main service models: (a) Infrastructure as a Service (IaaS), which provides virtualized computing resources like virtual machines and storage; (b) Platform as a Service (PaaS), which offers a platform for developing, running, and managing applications; and (c) Software as a Service (SaaS), which delivers ready-to-use software applications over the internet. The 'Allotment of electromagnetic spectrum' is a regulatory function managed by government bodies to assign radio frequencies for telecommunications and broadcasting, and it is not a service offered within the cloud computing model.