When might you need to use a dolly with a second trailer?

Answer: B — When connecting to a third trailer

Using a dolly with a second trailer is essential when connecting to a third trailer. A dolly serves as a connector between the second trailer and the third trailer, allowing for the proper distribution of weight and stability during transport. The dolly provides the necessary support and coupling mechanism required to secure the additional trailer for safe travel. In this context, routine maintenance checks usually do not involve the connections or operational elements of multiple trailers, and transporting oversized loads typically focuses on the load's dimensions rather than the type of equipment used for coupling. Reversing trailers also does not necessitate the use of a dolly, as it pertains more to maneuvering techniques rather than the coupling of multiple trailers. Consequently, the use of a dolly is specifically relevant when adding a third trailer to a combination set-up.