You are developing a user portal for a company. You need to create a report for the portal that lists information about employees who are subject matter experts...

Data Connect grants a more granular control and consent model: you can manage data, see who is accessing it, and request specific properties of an entity. This enhances the Microsoft Graph model, which grants or denies applications access to entire entities.
Microsoft Graph Data Connect augments Microsoft Graph's transactional model with an intelligent way to access rich data at scale. The data covers how workers communicate, collaborate, and manage their time across all the applications and services in Microsoft 365.
Incorrect:
Not B: The Microsoft Graph API is a RESTful web API that enables you to access Microsoft Cloud service resources. After you register your app and get authentication tokens for a user or service, you can make requests to the Microsoft Graph API.
A simplistic definition of a Graph API is an API that models the data in terms of nodes and edges (objects and relationships) and allows the client to interact with multiple nodes in a single request.
Not C: Microsoft Graph connectors, your organization can index third-party data so that it appears in Microsoft Search results.
With Microsoft Graph connectors, your organization can index third-party data so that it appears in Microsoft Search results.
Reference:
https://docs.microsoft.com/en-us/graph/data-connect-concept-overview