Universal Container’s HR manager requested the Salesforce Admin to have the employee social security field in Salesforce accessible only to the HR department. What would the Salesforce Admin do to restrict employee social security field access?

Answer options:

A.Use permission set
B.Use manual sharing
C.Use role hierarchy
D.Use field level security

Correct Answer: D 
Field level security can be used to restrict access to a field. It is usually used when you don’t want certain fields to be accessible to all users or you want to provide access to certain group of users. 
Option A is incorrect because permission set doesn’t restrict field access. 
Option B is incorrect because manual sharing is sharing a record with one user. 
Option C is incorrect because role hierarchy extends access for a manager, for example to access his team records. 
Reference: 

https://help.salesforce.com/articleView?id=admin_fls.htm&type=5