Which requirements must trailers with a gross weight of 3,000 pounds and less have?

Trailers with a gross weight of 3,000 pounds and less must have specific lighting and reflective indicators to ensure safety while on the road. The correct requirement includes having two rear reflectors and a stoplight.

These reflectors are crucial because they enhance visibility, especially during low-light conditions, helping other drivers to see the trailer from behind. The addition of a stoplight is equally important, as it provides a clear indication to vehicles following behind that the trailer is slowing down or stopping, which is essential for preventing collisions.

The other requirements listed, such as front clearance lamps, side marker lamps, and an automatic braking system, do not apply specifically to trailers within this weight classification as defined by safety and legal regulations. Therefore, the presence of two rear reflectors and a stoplight ensures compliance with the safety standards set for smaller trailers, making option B the most accurate answer.