Which of the following can be used to extend Sitecore’s functionality?

Custom pipelines are a powerful way to extend Sitecore's functionality because they allow developers to add their own processes into the Sitecore event lifecycle. Each pipeline is a series of steps that Sitecore executes in a defined order, enabling developers to inject custom logic or modify existing behavior at specific points in the request processing flow.

This extension capability is fundamental for customizing Sitecore, as developers can create new pipelines or modify existing ones to cater to specific business needs, such as data processing, validation, or resource management. By leveraging custom pipelines, developers can also ensure that their extensions are reusable and maintainable within the Sitecore framework.

While default templates and server configurations play important roles in Sitecore's operation, they do not inherently provide the same extensibility capabilities as custom pipelines. Default templates are used for content modeling, and server configurations are focused on environment setup rather than the dynamic customization of functionality. Sitecore modules can also extend functionality but may not always provide the same level of customizability and integration that pipelines offer. Therefore, the option of using custom pipelines is the most effective way to extend Sitecore's functionality.