What lights must a barge moored in a slip exhibit at night?

A barge that is moored in a slip does not have any specific light requirements at night, as long as it is not obstructing navigation. This is because its position is stationary and it does not represent a hazard to navigation in that environment.

According to the U.S. Coast Guard's navigation rules, vessels at anchor are typically required to display specific lights to signify their location to other vessels. However, the rules state that a vessel moored in a designated slip or docking facility does not need to exhibit any lights, meaning it can simply remain dark unless specified by local regulations or requirements for operational reasons.

The other options provided would suggest lighting arrangements appropriate for different scenarios. For example, two anchored lights would be applicable for a vessel at anchor in open waters, while a single white light is more commonly associated with vessels in distress. Similarly, red over green lights indicate a combination of a navigation and underway signal, which is not applicable to a barge that is legally secured in a slip.