Use All users can view price books and add them to opportunities. Users can add any product within that price book to an opportunity.

For Price Books, the typical access settings you can configure in the context of OWD are:

Public Read Only: This allows all users to view the price book entries but does not allow them to edit them. Users can add products from price books to opportunities, quotes, etc., as long as they have the necessary permissions to do so on those records.

Controlled by Parent: This setting is more common for objects that have a master-detail relationship, where access is determined by the parent record. However, it's not applicable to Price Books as they don't follow this pattern in a typical Salesforce implementation.

Given the context of your question and the standard Salesforce functionality, the correct answer would be:

A. Public Read Only

This setting would enable sales agents to see the products listed in the Price Books, which is necessary for adding products to opportunities, while still controlling edit permissions through other means, such as profile settings or permission sets specifically designed for users who need to edit Price Books....