A vertical rainwater leader installed inside the building is not required to have a cleanout if _______________________.

The correct choice is that a vertical rainwater leader installed inside the building is not required to have a cleanout if it discharges to daylight, above grade, through the outside wall. This is because when the rainwater leader discharges directly to the outside and is not connected to the building's drainage system that carries wastewater, the need for maintenance access is significantly reduced. If the water flows freely and visibly to the outside, any obstruction can be easily identified and managed externally.

Choosing this option aligns with plumbing codes that prioritize ease of maintenance and reduces the risk of blockage within the building. In instances where the discharge method is above grade and visible, the requirement for a cleanout is waived because the system can be monitored and cleared without additional access points inside the structure.

In contrast, other answers involve situations where additional complexity in piping exists or where maintenance might be necessary internally, thus requiring cleanouts for effective monitoring and servicing of the plumbing system.