You need to obtain the external data required for the Help Desk website. What should you use?

BDC Services provides a metadata model and secure connector framework that allows SharePoint sites to read and, optionally, write to external data sources including SQL databases, OData feeds, and web services without requiring custom code on every page. External lists and web parts on the Help Desk site can consume BDC models to display live external data. This is the architecturally correct SharePoint-native solution for integrating external data into a site.

An Office 365 REST endpoint is an API consumption pattern, not a SharePoint service application that manages connections and security for external data within an on-premises or hybrid SharePoint deployment.

Microsoft Power BI is a business analytics and data visualization platform; it is not a SharePoint service used to source or expose external data within a SharePoint site.

A Content Query web part aggregates content from within SharePoint site collections and cannot retrieve data from external systems outside of SharePoint.