Where may air conditioning equipment discharge, according to plumbing standards?

According to plumbing standards, air conditioning equipment typically should not be discharged into rainwater leaders, vent stacks, or through fixture tailpieces larger than 1-1/4 inches.

Discharging air conditioning equipment into rainwater leaders can lead to issues with drainage systems and complicate stormwater management. Similarly, using a vent stack for such discharges is not recommended because vent stacks are designed to allow for the escape of gases and odors, not to handle water or condensation from HVAC systems. This can create problems with pressure and functionality of the plumbing system.

Moreover, the tailpiece of plumbing fixtures, particularly when larger than 1-1/4 inches, is not intended to accept discharges from air conditioning equipment, as it is meant for the drainage of waste water specifically from fixtures.

All these considerations are critical in protecting the integrity of the plumbing system and ensuring compliance with plumbing codes and standards. Thus, none of the provided options are acceptable discharge points for air conditioning equipment.