Final answer:
The most significant hazard when a truck and trailer are turning right beside you is the trailer swinging wide into adjacent lanes during the turn.
Step-by-step explanation:
When a truck and trailer are turning right, the hazard you should watch out for the most is C) Trailer swinging wide. This is a common situation as trucks need to make wider turns. The behavior of the trailer can be unpredictable, and it may encroach into adjacent lanes, posing a risk to other vehicles. This is especially true in areas with tight turns and limited space. As such, giving the truck ample room to turn is important. Additionally, while it's essential to be mindful of pedestrians crossing (A), the immediate hazard in the context of the truck maneuvering beside you is the possibility of the trailer swinging wide.