According to the CPC, each plumbing fixture must be separately trapped by an approved water-seal trap. Under what exception may one trap serve multiple fixtures?

• One trap may serve any two fixtures of the same type if they are on the same floor.
• One trap may serve all fixtures in a residential bathroom group.
• One trap may serve fixtures if they discharge into a common waste line with a cleanout.
• One trap may serve up to three single-compartment sinks or laundry tubs in the same room within 30 inches of each other.