This is a purely RTT topic since it doesn't exist in car-based tests at all, and it's an area some riders underestimate because it feels like "just one more passenger."
Here is one worth locking in:
What is a rider legally required to ensure before carrying a pillion passenger?
The passenger must be seated properly on a proper pillion seat with footrests, and both rider and passenger must wear an approved helmet, properly fastened, not just worn loosely. Responsibility for the passenger's safety and correct positioning falls on the rider, not the passenger.
Beyond pillion rules, this category also covers how carrying a passenger changes braking distance and cornering behavior.
Your turn. If there is an RTT rule you keep mixing up, post it here. If you know the answer to someone else's, help them out.