Determine whether the following situations involved a duty of care.
a) A dentist unknowingly transmits the AIDS virus from one patient to the next, via his drill. Any possibility of spreading the virus could have been prevented if the drill has been specially treated between clients, but this was not common practice at the time.
b) An 11-year-old girl, riding a headstrong horse in parklands, collides with a group of pedestrians walking along a path. An adult rider would have been able to control the horse properly.