Universal Container has requested from the salesforce admin to set up Federation IDs to few users in the company. How can this ID be assigned?

Answer options:

A.Assign it through a permission set
B.Create a new profile related to the federation ID
C.Through the role hierarchy
D.Assign it when setting up a user account

 Correct Answer: D 
 You assign a Federation ID when setting up a user account. When you set up SSO on your production environment, you can assign the Federation ID for many users at once with tools like the Salesforce Data Loader. Federation ID is a unique username for each user that can be shared across multiple apps. Sometimes the ID is the user`s employee ID. The important part of the Federation ID is that it is not duplicated within a Salesforce org. But the user can have the same Federation ID for more than one Salesforce org. 
Option A is incorrect because a permission set is a collection of settings and permissions that give users access to various tools and functions. The settings and permissions in permission sets are also found in profiles, but permission sets extend users’ functional access without changing their profiles 
Option B is incorrect because a profile in Salesforce is a group/collection of settings and permissions that define what a user can do in Salesforce. 
Option C is incorrect because a role hierarchy works together with sharing settings to determine the levels of access users have to your Salesforce data.
Reference: 

https://help.salesforce.com/articleView?id=sso_about.htm&type=5&sfdcIFrameOrigin=null