Concept:Authorised road users are persons legally permitted to use public roads, including pedestrians, cyclists, and drivers or riders of vehicles.
Explanation:Pedestrians are allowed to use roads legally.
Bicycle riders are also allowed to use roads legally.
Tricycle riders are permitted road users as well.
Roller skaters are not generally considered authorised road users on public roads.
They are expected to use designated areas such as parks or skating rinks.
Therefore, roller skaters are the exception in this list.
Answer:C. roller skaters