Final answer:
Bicycles must be equipped with a red reflector on the back that is visible at night from a certain distance, usually around 100 feet or 30 meters.
Step-by-step explanation:
In order to ensure safety when riding a bicycle at night, it is required to have a red reflector on the back that is visible at a certain distance.
This distance can vary depending on the country or state, but generally, the reflector should be visible at a distance of at least 100 feet or 30 meters.
This ensures that other drivers or pedestrians can see the bicycle from a reasonable distance and take necessary precautions.