Explanation
Setting the Request object's OWD to Public Read/Write is the simplest and most efficient way to allow all employees to collaborate on requests. Option B is incorrect, since granting Modify All Data permission on all profiles would give too much access and affect other objects as well. Option C is incorrect, since creating a criteria-based sharing rule to share all records with all users would be redundant and inefficient. Option D is incorrect, since setting the OWD to Public Read Only would not allow users to edit requests3.

Explanation
The user who posted the file and users with access to the record can view the file by default, as files posted to a record's feed inherit the record's sharing settings3. Users with a shared chatter post link to the file will not be able to view the file by default, unless they also have access to the record. Only the user who posted the file will not be able to view the file by default, as other users who have access to the record can also view it.

Explanation
Enabling Community User Visibility is the best option to allow viewing chatter posts from all customers. Community User Visibility is a setting that allows community users to see and interact with other community users, regardless of their account or role2. Setting View All for Chatter posts, enabling Chatter Super User, and enabling Internal Users Visibility are not options that can achieve the same result.