What programming model is typically used to build Azure Functions?

The serverless computing model is the correct choice for building Azure Functions because this model abstracts the underlying infrastructure, allowing developers to focus on writing code without worrying about server management. In a serverless environment, resources are automatically provisioned and managed by the cloud provider, enabling scalable execution of functions in response to events. This means that applications can run in a highly efficient manner, scaling automatically according to demand.

In contrast, the desktop application model is focused on applications running on client machines, which doesn't apply to Azure Functions. The client-server model involves a direct relationship between clients making requests to servers handling those requests, which doesn't align with the serverless nature of Azure Functions. Similarly, multi-tier architecture describes a system architecture pattern that separates different layers for better organization and scalability, but again it doesn't specifically address the unique operational characteristics of serverless computing that Azure Functions exemplify.