A company has a private sharing model in place and one of the sales users is having issues in accessing a type of record they need. This sales user is located at the bottommost of the role hierarchy. What is the best approach to give the user access?

Answer options:

A.Role Hierarchy
B.Field Level Security
C.Sharing Rules
D.Organization-Wide Default

Correct Answer: C 
Use sharing rules to extend sharing access to users in public groups, roles, or territories. Sharing rules give particular users greater access by making automatic exceptions to your org-wide sharing settings. You can do this based on a sharing rule on record ownership or other criteria. After you select which records to share, you define which groups or users to extend access to and what level of access they have. 
Option A is incorrect because the role hierarchy automatically grants record access to users above the record owner in the hierarchy. 
Option B is incorrect because field level security controls whether a user can see, edit, and delete the value for a particular field on an object. 
Option D is incorrect because organization wide default is baseline settings in Salesforce which specify which records can be accessed by which user and in which mode. 

https://trailhead.salesforce.com/en/content/learn/modules/data_security/data_security_sharing_rules