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 .

Explanation
Creating a Permission Set that grants "View All" permission for Opportunity is the best approach to meet the requirements. This will allow the Sales Reporting team to view all Opportunity records without changing their profile or OWD settings. Creating a Permission Set that grants "View All Data" permission would give them access to all data in the org, which is not necessary. Making Opportunity OWD read-only would affect all users in the org, which may not be desirable. Giving "View All Data" permission to the Sales Reporting Profile would also give them access to all data in the org, which is not necessary

Explanation
Creating a protected custom metadata type that stores the encryption key and packaging it with its associated records in a managed package is the best way to securely store the confidential key, as protected custom metadata types are only accessible within the package namespace and cannot be viewed or modified by subscribers2. Creating a protected custom metadata type and packaging it in an unlocked package will not work, as unlocked packages do not support protected custom metadata types3. Creating a custom metadata type and restricting access to the admin profile will not work, as users with View Setup permission can still view the custom metadata type and its records.

Explanation
According to this source, Apex managed sharing is the best way to share records based on complex logic that can't be handled by declarative sharing. In this case, the architect can use Apex code to create a trigger on the Job Interview object that will create a share record for the interviewer user when the lookup field is populated.
The other options are not feasible or scalable.