Explanation
Organization-wide defaults (OWD) are a way to set the baseline level of access for each object in the organization. OWD can be set to Private, Public Read Only, Public Read/Write, or Public Read/Write/Transfer for different objects. In this case, setting OWD to Public Read Only for Lead object will allow all full-time internal employees to view all leads, but not edit them. A subset of employees can be granted additional access to leads using other mechanisms such as profiles, permission sets, or sharing rules. Therefore, the answer B is correct and the other options are incorrect .