Under what condition may electrical outlet boxes not require drilling for conduit entrance?

The correct choice is based on the functionality and design of electrical outlet boxes. When an outlet box is provided with knockouts, it means that the box has pre-formed openings designed for the easy entry of conduits. These knockouts allow for a clean and National Electrical Code-compliant way to connect electrical conduits without the need for drilling additional holes in the box itself. This feature ensures that the boxes maintain their structural integrity and are installed safely.

In contrast, vertical mounting, covers, or larger openings do not inherently eliminate the need for drilling conduit entrances. The presence of knockouts specifically addresses the need for a proper entry point without modification to the box, which is crucial for maintaining electrical safety standards. This emphasizes the importance of using properly designed components in electrical installations.