Microsoft Certified: Security, Compliance, and Identity Fundamentals

A developer is designing a web application and needs to verify that each person signing in is genuinely who they claim to be before any access decisions are made. Which identity concept describes this specific step, and which protocol does the Microsoft identity platform use to handle it?

An organization runs several internal apps, each currently maintaining its own username and password store, which is costly to manage as staff join and leave. Management wants users to sign in once and be automatically signed in to all apps that share the same directory. Which capability, enabled by delegating to a centralized identity provider, achieves this?